add separate is:buried and use with filtered deck
env var to skip expensive closing during dev
bury card option
skip startup sync when restoring from backup
catch invalid temp folder and other tweaks

- tweak sync code so that a failure in loading the collection
  won't leave the app with an unopen collection
- don't show corrupt collection message when the error is not
  a db error
- catch the temp folder issue when loading the collection. i suspect
  this was the issue that was causing some people to end up with
  an open anki instance with no collection loaded
Merge remote-tracking branch 'dae/master' into develop-flake

Conflicts:
	anki/db.py
	anki/find.py
	aqt/errors.py
	aqt/main.py
	aqt/reviewer.py
Re-flake.
Use the less ambiguous “except ExceptionNN as e:” instead of “except ExceptionNN, e:”
(We require python>=2.6 anyway.)