Update reference to old "autotype" setting

Should be schema.default
Check cluster.partition in part vlabel creation

VertexLabelMaker now checks that cluster.partition is true in the
graph configuration when it creates a label with `partition()`
enabled.  Part of #706.

This makes the related cluster.partition check in
`StandardTitanTx.addVertex` redundant for new installations, though
0.5.0 installs could have defined a partitioned vertex label on a non
cluster.partition'ed backend.
Removing cluster.partition check in tx.addVertex

Part of #706; Preceding commit
6941008da884bedde58dd516d19e5090c55f7811 has moved this check up to
schema definition time, making the check inside addVertex mostly
redundant (and entirely redundant on new installs).
Warn and return null for illegal getVertex(id) arg

Since this method is part of the Blueprints API, it should probably
return null instead of throwing IllegalArgumentException for the
(Titan-specific rather than Blueprints-standardized) range of IDs
which are outside the legal vertex ID space.  This commit changes the
exception type thrown in IDManager.getUserVertexIDType to
InvalidIDException, which inherits from TitanException and in turn
RuntimeException.  StandardTitanTx.getVertex catches
InvalidIDException, logs a warning, and then returns null.

I think nothing needs to be done to make bogus schema vertex IDs
return null, since they follow a different logic path in
IDManager.getKey that just converts the long into a byte buffer.  Not
sure though.
Update partitioned-vertex-label tests

This is a consequence of 628d48fe23431422e71225306ce2220611a45c86.
One of the test methods in TitanBaseGraphTest creates a partitioned
vertex label, but the ability to create these is now dependendent on
whether cluster.partition is true.  I made the label in
TitanBaseGraphTest non-partitioned moved the partitioned-vertex-label
related assertions to a smaller method in TitanPartitionGraphTest.
Always close IndexReaders in LuceneIndex.mutate

For #761
Enable BP supportsThreadIsolatedTransactions

Reflectively lookup and set this Blueprints Features field to true
when it exists, otherwise log and fail silently.  This is done
reflectively for transparent compatibility with 2.5.0 and 2.6.0
without having to recompile (it exists in the latter but not in the
former).
Dependency management tweaks for BP 2.6.0

Titan is still on BP 2.5.0 after this commit.  This commit just adds
some dependencyManagement bits to the poms to allow changing the
version to 2.6.0 for testing without causing convergence errors.