Fix ClassCastException in AbstractVertexCentricQueryBuilder

Addresses https://github.com/thinkaurelius/titan/issues/651

Add a check for Conditions to ensure they can be casted to PredicateCondition
before attempting the cast while looking for equality constraints in the
AbstractVertexCentricQueryBuilder
Merge pull request #653 from mgmuscari/fix-query-builder

Fix ClassCastException in AbstractVertexCentricQueryBuilder
Prefer forward-compatible API in perf tests

tx.getVertex("foo", 42L) is going away in titan05, but
Iterables.getOnlyElement(tx.getVertices("foo", 42L)) is functionally
equivalent and exists in both master and titan05.
Add failing test for edges exceeding tx-cache-size

There seems to be buggy behavior when the number of edges on a vertex
exceeds the tx-cache-size number. If you remove an edge from the vertex,
it can reappear when you call getEdges on the vertex. I added a unit
test which demonstrates this.
Merge branch 'solongordon-failing-delete-edge-test'
Add *.DS_Store to .gitignore
Merge branch 'mikedias-patch-1'

Fixes #675
fix typo and wrong db product mention.
fix up javadoc in KeyColumnValueStore.getSlice
Merge pull request #690 from anvie/master

Fix typo and javadoc
Update recovery.txt
Update partitioning.txt
Removing AsciiDoc files intended for titan05