gitk: Add a user preference to enable/disable use of themed widgets
gitk: Add a user preference to enable/disable use of themed widgets

Also move the hide-remotes option up into the commit display options
in the Edit->Preferences panel, since it affects the commit display
more than the diff display.

Signed-off-by: Paul Mackerras <19a0ba370c443ba08d20b5061586430ab449ee8c@samba.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git