git-p4: Add copy detection support

git-p4: Add copy detection support

Add new config options:
    git-p4.detectCopies         - Enable copy detection.
    git-p4.detectCopiesHarder   - Find copies harder.
The detectCopies option should be set to a true/false value.
The detectCopiesHarder option should be set to true/false value.
P4Submit can now process diff-tree C status and integrate files accordingly.

Signed-off-by: Vitor Antunes <vitor.hda@gmail.com>
Acked-by: Pete Wyckoff <pw@padd.com>
Acked-by: Tor Arvid Lund <torarvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>