Merge branch 'install_issues'

 to explain why this merge is necessary,
Merge branch 'tray_inbox_unread_indicator'
Merge branch 'translations'
Merge branch 'master' of https://github.com/Bitmessage/PyBitmessage into translations
Corrected Russian translation.
Ignore, and don't save to memory, messages larger than 20MB (temporary)
Merge pull request #637 from Atheros1/master

Ignore, and don't save to memory, messages larger than 20MB (temporary)
Merge pull request #629 from yurivict/translations

Corrected Russian translations (e->ё, commas, spelling, formal style)