improved mongodb authentication

Signed-off-by: Wouter Vroege <wouter@woutervroege.nl>
Merge branch 'refs/heads/mongo'
Merge remote-tracking branch 'upstream/master'

Signed-off-by: Wouter Vroege <wouter@woutervroege.nl>

Conflicts:
	lib/shared/backends/mongo.js
beautifying...

Signed-off-by: Wouter Vroege <wouter@woutervroege.nl>
added a newline

Signed-off-by: Wouter Vroege <wouter@woutervroege.nl>
Merge pull request #72 from woutervroege/carddav-mongo

improved mongodb authentication