Encode full commit message parameter as UTF-8 Base64

The full commit message may contain characters that cannot be
properly escaped.

To avoid this, encode the message in Base64.  Also make sure that
the text is UTF-8.

Change-Id: Iae0973886a4871acf041da420619887655dbfb29
Tidy up comments in GerritTrigger.java

Change-Id: Idc2c7fce752b3d7d4c62ab57616baba162721688
Lowering log level of Notifying listener

The introduction of triggering of comment added has
caused the FINE loglevel to be close to unreadable.
Lowering the level to FINEST a.k.a. trace should
mediate that.

Change-Id: I33adf5471f5e8e5b66a748a663d48c3c26122729
Merge branch 'i' of gerrit-trigger-plugin

Conflicts:
	gerrithudsontrigger/src/main/java/com/sonyericsson/hudson/plugins/gerrit/trigger/hudsontrigger/GerritTrigger.java