Windows porting all day. Fixed a lot of issues with the webapp,
so quite productive. Except for the 2 hours wasted finding a way to kill a
process by PID from Haskell on Windows.

Last night, made `git annex metadata` able to set metadata on a whole
directory or list of files if desired. And added a `--metadata field=value`
switch (and corresponding preferred content terminal) which limits
git-annex to acting on files with the specified metadata.