Add 'git-p4 commit' as an alias for 'git-p4 submit'

Given that git uses 'commit', git-p4's 'sumbit' was a bit confusing at times;
often making me do 'git submit' and 'git-p4 commit' instead.

Signed-off-by: Marius Storm-Olsen <marius@trolltech.com>
Acked-By: Simon Hausmann <simon@lst.de>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

contrib/fast-import/git-p4

@@ -1651,6 +1651,7 @@ def printUsage(commands):
 commands = {
     "debug" : P4Debug,
     "submit" : P4Submit,
+    "commit" : P4Submit,
     "sync" : P4Sync,
     "rebase" : P4Rebase,
     "clone" : P4Clone,