git-subtree: Added the 'subtree add' command to the shell and proc and implemented the interface features for the dialog. Still have to write the actaul call that does the work when you press ok.

Also added a method in the local file browse dialog to support only seeing the subtree from a specified root.

Signed-off-by: John Butterfield <johnb003@gmail.com>
Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
git-subtree: Added initial support for the 'git subtree add' command.

Signed-off-by: John Butterfield <johnb003@gmail.com>
Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>

Conflicts:
	src/TortoiseProc/SubtreeAddDlg.cpp
Added support for 'git subtree push', and 'git subtree pull'.

Signed-off-by: John Butterfield <johnb003@gmail.com>
Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Converted some strings to resources and general code cleanup

Signed-off-by: John Butterfield <johnb003@gmail.com>
Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>