Correct bundle, provider names to be consistent

Technically our project name is "JGit", not "Java Git".  In fact
there is already another project called "JavaGit" (no space) that we
don't want to become confused with.  Ensure we always call ourselves
"JGit" in user visible assets, like the bundle name.

Other Eclipse products list their provider as "Eclipse.org",
not "eclipse.org".  So list ourselves that way in all of our
plugin.properties files.

Change-Id: Ibcea1cd6dda2af757a8584099619fc23b7779a84
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>