add bonus data feature to imgdiff/imgpatch/applypatch

The bonus data option lets you give an additional blob of uncompressed
data to be used when constructing a patch for chunk #1 of an image.
The same blob must be available at patch time, and can be passed to
the command-line applypatch tool (this feature is not accessible from
edify scripts).

This will be used to reduce the size of recovery-from-boot patches by
storing parts of the recovery ramdisk (the UI images) on the system
partition.

Change-Id: Iac1959cdf7f5e4582f8d434e83456e483b64c02c