run Rat consistently for all maven assemblies

Make all assemblies and RAT testing of those assemblies work the same way (convention over configuration). Have common parent POM concerned with doing assemblies, and have the 3 distribution poms (that build the base, uima-as, and sandbox distributions) use this as a common parent.

Builds are done in the "package" lifecycle.

After build is done, in the "verify" lifecycle (just before "install), run the RAT tool. Incorporate into the distribution POMs the set of RAT exclusions. Include a step of unpacking the assemblies (because the RAT tool doesn't work on zips).

Running mvn install will now do the assemblies and do the RAT testing. This effectively automates future RAT testing.

Running mvn install on the new superPom for distributions will build all 3 distributions (base, sandbox, and uima-as, not uima-cpp).

Insure the assemblies are not uploaded to the maven repo's - (they're big, not jars, and should instead be downloaded from our website).

After this change, to build distributions, do mvn install, not mvn assembly:assembly, on the distribution POMs. Cripple mvn assembly:assembly so some kind of error message comes out reminding to use mvn install instead.

Update website with new instructions on building distributions.