Add ext2, ext3, and vfat to releasetools

Support some non-standard partition that may be found in recovery.fstab

Change-Id: I0026a1d3ae5d432db10150d1a15f7bc8e7a6054b
CWR does not support writing a partition from memory. Use /tmp to store the extracted file, then write it.
Add otapackage support for backuptool

Change-Id: I512554c579d444067cd3ccbb0e6946a5eb6bc964a
Allow override of device asserts, including multi-device support.

Set in board file with TARGET_OTA_ASSERT_DEVICE.
(cherry-picked from commit 0f452f21fc9323b9d1fe746161761cf40aaa5030)

Change-Id: I3d06bdc0e3e26bde0c0e646accd050364f9713b9