repo 1.0.7

Remove import_tar, import_zip and the <snapshot> elements

Now that repo relies only on the git data stream (as it is much
faster to download through) we don't really need to be parsing the
<snapshot> elements within manifest.  Its a lot of complex code to
convert the tar (or zip) through to a fast import stream, and we
just aren't calling it anymore.

Signed-off-by: Shawn O. Pearce <sop@google.com>