Description of problem:
The jcr2vfs migration tool is broken. It can't migrate certain asset types, because of classpath order issues. There are both Drools 5.x and Drools 6.x on the CP at the same time, which causes serious issues during runtime. See for example following exception thrown by the tool:

**********************************************************************
java.lang.NoSuchMethodError: org.drools.core.util.IoUtils.readBytesFromInputStream(Ljava/io/InputStream[B
at org.drools.compiler.kie.builder.impl.KieFileSystemImpl.write(KieFileSystemImpl.java:47)
at org.guvnor.common.services.builder.Builder.visitPaths(Builder.java:551)
at org.guvnor.common.services.builder.Builder.<init>(Builder.java:118)
at org.guvnor.common.services.builder.LRUBuilderCache.assertBuilder(LRUBuilderCache.java:88)
at org.guvnor.common.services.builder.LRUBuilderCache$Proxy$$$_WeldClientProxy.assertBuilder(LRUBuilderCache$Proxy$$$_WeldClientProxy.java)
at org.kie.workbench.common.screens.datamodeller.backend.server.DataModelerServiceImpl.getProjectClassLoader(DataModelerServiceImpl.java:475)
at org.kie.workbench.common.screens.datamodeller.backend.server.DataModelerServiceImpl.generateModel(DataModelerServiceImpl.java:281)
at org.kie.workbench.common.screens.datamodeller.backend.server.DataModelerServiceImpl.saveModel(DataModelerServiceImpl.java:238)
at org.kie.workbench.common.screens.datamodeller.backend.server.DataModelerServiceImpl.saveModel(DataModelerServiceImpl.java:217)
at org.kie.workbench.common.screens.datamodeller.backend.server.DataModelerServiceImpl$Proxy$$$_WeldClientProxy.saveModel(DataModelerServiceImpl$Proxy$$$_WeldClientProxy.java)
at org.drools.workbench.jcr2vfsmigration.migrater.asset.FactModelsMigrater.migrate(FactModelsMigrater.java:120)
at org.drools.workbench.jcr2vfsmigration.migrater.asset.FactModelsMigrater$Proxy$$$_WeldClientProxy.migrate(FactModelsMigrater$Proxy$$$_WeldClientProxy.java)
at org.drools.workbench.jcr2vfsmigration.migrater.AssetMigrater.migrate(AssetMigrater.java:190)
at org.drools.workbench.jcr2vfsmigration.migrater.AssetMigrater.migrateAll(AssetMigrater.java:158)
at org.drools.workbench.jcr2vfsmigration.migrater.AssetMigrater$Proxy$$$_WeldClientProxy.migrateAll(AssetMigrater$Proxy$$$_WeldClientProxy.java)
at org.drools.workbench.jcr2vfsmigration.Jcr2VfsMigrater.migrateAll(Jcr2VfsMigrater.java:91)Migration ended with warnings. Written into outputVfsRepository (

).
at org.drools.workbench.jcr2vfsmigration.Jcr2VfsMigrater$Proxy$$$_WeldClientProxy.migrateAll(Jcr2VfsMigrater$Proxy$$$_WeldClientProxy.java)
at org.drools.workbench.jcr2vfsmigration.Jcr2VfsMigrationApp.migrate(Jcr2VfsMigrationApp.java:64)
at org.drools.workbench.jcr2vfsmigration.Jcr2VfsMigrationApp.run(Jcr2VfsMigrationApp.java:52)
**********************************************************************

java.lang.ClassCastException: org.drools.core.base.accumulators.BigDecimalSumAccumulateFunction cannot be cast to org.drools.runtime.rule.AccumulateFunction
at org.drools.compiler.PackageBuilderConfiguration.loadAccumulateFunction(PackageBuilderConfiguration.java:530)
at org.drools.compiler.PackageBuilderConfiguration.buildAccumulateFunctionsMap(PackageBuilderConfiguration.java:479)
at org.drools.compiler.PackageBuilderConfiguration.init(PackageBuilderConfiguration.java:194)
at org.drools.compiler.PackageBuilderConfiguration.<init>(PackageBuilderConfiguration.java:165)
at org.drools.guvnor.server.builder.BRMSPackageBuilder.getPackageBuilderConfiguration(BRMSPackageBuilder.java:134)
at org.drools.guvnor.server.builder.BRMSPackageBuilder.<init>(BRMSPackageBuilder.java:67)
at org.drools.workbench.jcr2vfsmigration.migrater.asset.GuidedEditorMigrater.migrate(GuidedEditorMigrater.java:92)
at org.drools.workbench.jcr2vfsmigration.migrater.asset.GuidedEditorMigrater$Proxy$$$_WeldClientProxy.migrate(GuidedEditorMigrater$Proxy$$$_WeldClientProxy.java)
at org.drools.workbench.jcr2vfsmigration.migrater.AssetMigrater.migrate(AssetMigrater.java:192)
at org.drools.workbench.jcr2vfsmigration.migrater.AssetMigrater.migrateAll(AssetMigrater.java:158)
at org.drools.workbench.jcr2vfsmigration.migrater.AssetMigrater$Proxy$$$_WeldClientProxy.migrateAll(AssetMigrater$Proxy$$$_WeldClientProxy.java)
at org.drools.workbench.jcr2vfsmigration.Jcr2VfsMigrater.migrateAll(Jcr2VfsMigrater.java:91)
at org.drools.workbench.jcr2vfsmigration.Jcr2VfsMigrater$Proxy$$$_WeldClientProxy.migrateAll(Jcr2VfsMigrater$Proxy$$$_WeldClientProxy.java)
at org.drools.workbench.jcr2vfsmigration.Jcr2VfsMigrationApp.migrate(Jcr2VfsMigrationApp.java:64)
at org.drools.workbench.jcr2vfsmigration.Jcr2VfsMigrationApp.run(Jcr2VfsMigrationApp.java:52)
at org.drools.workbench.jcr2vfsmigration.Jcr2VfsMigrationApp.main(Jcr2VfsMigrationApp.java:37)
**********************************************************************

Version-Release number of selected component (if applicable):
6.1.0.DR3

How reproducible:
Always

Steps to Reproduce:
1. Simply run the tool against Guvnor 5.x repo that has DRL or BRL assets.

Actual results:
Exceptions during the migration (see above).

Expected results:
The migration should be successful.