git-gui: Minor UI layout improvements for console windows.

git-gui: Minor UI layout improvements for console windows.

Moved the Close button over to the lower right corner where our
Cancel/Save buttons are in the options dialog.  This should fit
better with our own look and feel as well as that of most apps
on Mac OS X and Windows.

Also set the lower status bar in a console window to indicate the
process is working and that the user should wait for it to finish.

Signed-off-by: Shawn O. Pearce <redacted>