Fix RFC 6122 implementation

JID resourceparts should be able to contain "@" and "/" characters
"example.net/@/" should be a valid JID.

Retab JID file
Allow JIDs such as "example.net/@"
Update/improve German translations
cleaned up avatar / tile creation
fixed potential npes in message parser
clean up getProposedNick
safety net in joinMuc
Merge branch 'development' of https://github.com/siacs/Conversations into development
Merge pull request #743 from weiss/update-german-translations

Update/improve German translations
Merge pull request #740 from SamWhited/jidrpfix

Fix RFC 6122 implementation
fixed another npe in hasBookmark
worked around concurrent modification exception
Make sure SASL tokenizer strips strings

Fix DIGEST-MD5 auth (make sure we're not splitting on BASE64 `==')
Merge pull request #744 from SamWhited/development

Fix DIGEST-MD5 auth
made muc parser more compatible with legacy mucs?! (whatever that is exactly)
set nick and autojoin=true for new bookmarks
refactored the message adapter a bit
further npe checks
display proper error in edit account details if jid is invalid