Update German language
Update German language

deleted 'pref_about_message'
more npe checks in muc packet parser
made presences synchronized
Merge pull request #653 from kriztan/patch-2

Update German language
fixed possible npe when loading null counterpart into message
Merge branch 'development' of https://github.com/siacs/Conversations into development
Added check for empty from on group chat packet
Merge pull request #664 from squidpickles/development

Added check for empty from on group chat packet
Add SCRAM-SHA1 support

Factor out GS2 tokanization into own class
Add authentication exception class

Fixes #71