Add questions about blah sync in blah setup

Will now ask user if information pertinent for blah sync should be
collected and configured
Remove preview functionality from blah

The preview functionality as it already existed was ill-conceived and
poorly executed.

What should the preview functionality do? Preview an unpublished post
seems the most logical think, but that was not what the code was doing,
since it assumed it would go into src (where only published stuff lives)
and then do a make with a target.

Future attempts may try to include a preview/% target in the makefile,
which should then depend on a post in the draft dir, and have a separate
output directory, but that will be pushed into the future.
Add blah sync functionality

If configured during setup (or manually after the fact) syncing
functionality now work.

Many more tests should be run, but it looks very good so far.

Also add .EXIT-CODES, documenting what the various blah exit codes means
and possible things to do to rectify the problem.