git p4: add support for 'p4 move' in P4Submit

For -M option (detectRenames) in P4Submit, use 'p4 move' rather
than 'p4 integrate'.  Check Perforce server for exisitence of
'p4 move' and use it if present, otherwise revert to 'p4 integrate'.

[pw: wildcard-encode src/dest, add/update tests, tweak code]

Signed-off-by: Gary Gibbons <ggibbons@perforce.com>
Signed-off-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>