Add hard titan-hbase log4j and slf4j-log4j12 deps

The HBase client depends on both log4j and its slf4j binding.  Unlike
the rest of Titan's modules, we can't make these artifacts optional in
titan-hbase.  This commit makes them mandatory and compile-scoped in
titan-hbase alone.

HBase references:

* https://issues.apache.org/jira/browse/HBASE-2608
* http://hbase.apache.org/book/config.files.html#client_dependencies