Re-think catalina/tomcat dependencies so as it is possible to build without tomcat7 API

It is not possible (or I'm doing something wrong) to build mod_cluster Tomcat libs with Tomcat 8-only API.
I hit this problem with RPM build on Fedora where I cannot download random stuff from maven central and I need to specify dependencies beforehand.

Description

• container/catalina contains calls to API that is deprecated in Tomcat 7 and missing in Tomcat 8, so I have to apply this patch: MODCLUSTER-528-CatalinaContext.java.patch before build
• profiles and test dependencies and Servlet API dependencies needs hacks to build without Tomcat 7 too: see other patches in mod_cluster-fedora-packages/

Suggestion

• architecture dependencies so as it is possible to build mod_cluster with Tomcat 8 API only (and Tomcat 7 API only)
• drop Tomcat 6 and JBossWeb from 1.3.x as they are not used in 1.3.x anyway (last use of Tomcat 6 and JBossWeb is 1.2.x)

Fedora 24 offers only Tomcat 8

...so does it even make sense to offer users Tomcat 7 libs RPM? At the moment, I have it disabled. Note: Former mod_cluster RPM (1.2.6) hasn't been distributing any usable tomcat integration; it has been AS7/JBossWeb one.