Update German language
Update German language

deleted 'pref_about_message'
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
basic arbitrary file transfer
bug fixes and various improvements for file transfer
copy non local files to private storage first
progress for http images as well. fixed open button for sent files
support for pgp files
some mime and pgp fixes for file transfer
progress for ibb transfers
adepted conversationadapter to deal with files
made file transfers cancelable