Title: Migrating Client Application APIs from 6.0.x to 6.1

Describe the issue:

• The "/execute" operation for REST remote API has seen some changes which should be included in the Migration Guide. Some of the changes are mentioned in this KCS [1] for your reference. Here I quote it's contents for your quick reference. Please review them and try to incorporate them in the mainstream documents like Migration Guide.
  ~~~
  If you are using BPM Suite 6.1 notice that the API has changed. Users of the remote API should not be affect by these details. Here is the list of changes:

The endpoint changed to /execute;
For the client we now must use the org.kie.remote.jaxb.gen package classes which are in the org.kie.remote:kie-remote-client artifact;
The client artifacts will only accept commands from this package, for other packages we will have errors and will not allowed to send commands;
The deployment ID is set using a new HTTP header Kie-Deployment-Id that is also available using the Java constant JaxbSerializationProvider.EXECUTE_DEPLOYMENT_ID_HEADER.

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[1] https://access.redhat.com/solutions/909913

Suggestions for improvement:

• Please update the Migration Guide with the changes suggested above.

Additional information:

• Nothing