Restore the "ignore directory" feature

Bring back the option for setting up routers to be
ignored persistently (across rug restarts). Rename
some of the internal data structures in the workers
to differentiate between routers in "debug" mode,
where they are ignored temporarily, and this persistent
ignore mode.

Change-Id: Idc2216bb8eb49384dc579ebc4180f6a193f535b6
Close a hole in debug mode

If we have routers in the work queue when we put them in debug mode,
skip any upcoming operations on them.

Change-Id: Idd6e92d3cb3c8e50a7b9807b5bad48c19d45511c
Merge pull request #95 from dhellmann/feature/restore-ignore-directory

restore ignore directory option