Reduce illegal vertex ID log message severity

Following comment by @mbroecheler on #727
Merge branch 'titan05' of github.com:thinkaurelius/titan into titan05
Kerberos+HBase+MapReduce authentication support

This commit adds support for HBase's authentication token system,
which is required for MapReduce (Titan-Hadoop/Faunus) jobs that want
to talk to a Kerberized HBase instance.

This commit has no effect on Kerberized HBase authentication outside
of MapReduce/Titan-Hadoop/Faunus, which works as described in the
HBase manual.

This commit was tested on CentOS 5, RHEL 6, and MIT Kerberos 1.8.x.
The Titan-Hadoop HBase read and write logic use different code and
config keys.  The read path uses HBase's own input format and config
keys, while the write path uses a custom format brought in with
Faunus.

When writing without HBase configuration files (including
hbase-site.xml) on the classpath of the MR tasks, the Titan-Hadoop
config setting
titan.hadoop.output.conf.ext.hbase.security.authentication should be
set to Kerberos.  This tells the HBaseStorageManager that starts up
inside the Titan-Hadoop write path to check for a Kerberos
authentication delegation token.  If an hbase-site.xml containing the
hbase.security.authentication=kerberos setting is on the MR task
classpath, then there's no need to duplicate it in the Titan-Hadoop
config file like this.

The read path just needs that setting on the submitting process's
classpath.
Merge branch 'titan05' of github.com:thinkaurelius/titan into titan05
Adding concurrent getSlice stress KCVS tests

I dislike nondeterministic tests like these in general, but they do
have the potential to detect a hypothetical race condition that leads
to a correctness failure.
Rewrote Titan-Hadoop incremental loading docs

This feature has been restored as of
bf39926f3f10ad8aacb16971d545c8595894e88c, but without documentation.
Incremental loading is now documented in roughly the same place as it
used to be in 0.4.4 (under the Titan I/O format docs), but the prose
and code examples have been rewritten from scratch.
Tweak default cassandrathrift connection pool settings

This commit disables the maxTotal parameter on the connection pool.
The connection pool size is now regulated through the maxActive and
maxIdle parameters on the pool.  Setting maxTotal appears to cause
commons-pool to repeatedly just barely exceed the limit by one
connection, then close 15% of the total pool size before repeating the
process.  The overall number of connections stays at or just one over
the configured limit, which is good, but routinely closing and
reopening connections can lead to a tens of thousands of TIME_WAIT
sockets in test scenarios with just one client and one server on the
same physical host, which is bad.

Keeping maxTotal off (negative) and using the active and idle limits
instead seems to avoid this behavior.  I've seen this before when
testing Titan-Hadoop and worked around it there by overridding the
defaults just for the affected Titan-Hadoop testsd.  Now I'm seeing it
again in ThriftGraphTest's getSlice stress tests, and I'm changing the
defaults instead of just working around it in a specific test config.
Prepping changelog for 0.5.1

This commit attempts to summarize changes between the 0.5.0 tag and
titan05 as of 88a06b1045d0d3e2bc047a46b1002a50b5059fc1 (Oct 1 before
the Solr merge).
Copy commented Titan-Hadoop config tips

The stock config file conf/hadoop/titan-graphson.properties had a note
about overridding Hadoop configuration settings along with some
commented suggested Hadoop config key-value pairs to consider.  This
commit copies that chunk of comments to the other stock Titan-Hadoop
config files.

This should be templated one way or another so that we don't have to
maintain a bunch of copies of the same chunk of text.
Tool to generate config files from ConfigOptions

Based on some feedback, I wanted a file templating facility that would
let me both automatically annotate settings in the stock config files
with ConfigOption information (like the description string and
mutability level), but also do more pedestrian templating tasks, like
including other files.

The ConfigOption bit is probably possible with Velocity, but it seemed
non-trivial or clumsy enough to implement with VTL that I just wrote a
one-file tool to do the job instead.