* Switch to using .git/annex/othertmp for tmp files other than partial
downloads, and make stale files left in that directory when git-annex
is interrupted be cleaned up promptly by subsequent git-annex processes.
* The .git/annex/misctmp directory is no longer used and git-annex will
delete anything lingering in there after it's 1 week old.
Also, in Annex.Ingest, made the filename it uses in the tmp dir be
prefixed with "ingest-" to avoid potentially using a filename used by
some other code.
