Added support for whitespace ignoring

Added support for whitespace ignoring

JGit did not have support for skipping whitespace when comparing
lines in RawText objects. I added a subclass of RawText that skips
whitespace in its equals and hashCode methods. I used a subclass
rather than adding functionality into RawText so that performance
would not be impacted by extra logic.

This class only supports ignoring all whitespace. Others will follow
that allow other forms of whitespace ignoring.

Change-Id: Ic2f79e85215e48d3fd53ec1b4ad13373dd183a4a