A new Expect-based release archive test

I'm trying this out.  When running "mvn verify -Paurelius-release" in
titan-dist-berkeleyje, an integration test extracts the distribution
zipfile and runs an Expect script that spawns gremlin.sh and runs a
few trivial commands (adds a vertex and commits it).  If any of the
expect subcommands timeout or don't see what they want, then the
script exits with nonzero status and the integration test fails, in
turn failing the verify lifecycle stage for the module.
Made Expect test backend-agnostic

What was BerkeleyIT.java in the previous commit is now
SingleVertexIT.java.  The specifics of the storage backend are passed
from the Maven pom through a properties file to the test at runtime.
Add expect-based gremlin test to 2 more distros
Merge branch 'master' of github.com:thinkaurelius/titan
Splitting titan-dist logic into two poms

This simplifies the child poms substantially and reduces the overall
number of copy-pasted lines in the dist poms.  It's a little bit hacky
but it seems to work.
Merge branch 'master' of github.com:thinkaurelius/titan
Adding Expect-script testing to distro assemblies

When -Paurelius-release is set, Expect scripts will unzip each of the
distributions (except HBase) and try running some trivial scripts
interactively using the unzipped assembly's gremlin.sh and
backend-appropriate Titan properties files.

This is executed during the using maven-failsafe-plugin during the
"verify" phase of the Maven lifecycle.
Removing conflict-prone stubs from bin

Fixes #422
Remove redundant path element from cassandra cfgs
Merge branch 'master' of github.com:thinkaurelius/titan