Add otapackage support for backuptool

Change-Id: I512554c579d444067cd3ccbb0e6946a5eb6bc964a
Update ota_from_target_files
releasetools: backup
I can't dance; I missed a two-step
cleanbuild: add *.zip.md5sum to installclean_files

Change-Id: I4b68bb9a8d421a54b008c5318fa82ed230bd6441