Added metadata entries to zipped bugreport:

- version.txt: bugreport format version
- main-entry.txt: name of the entry containing the main bugreport (flat file)

Also documented the zip format versions on bugreport-format.txt.

BUG: 26910355
BUG: 26639621

Change-Id: I76b9f6d330c36ad554fae8e691c9ea3ab3c97edd
2 files changed