Alternative hook to send email notifications.

This is coppied from git://git.gnome.org/sysadmin-bin
659d3981771751fc20a3f4e675485111589d69f6
First cleaning
Move gnome plugin
Remove gnome thinks
Automatic conversion to python3
Convert encoding/decoding of strings to python3
Send information about notes

Notes can be treated in the same way as branches. The only difference is
that they are rooted at refs/notes/*
Thread messages from single push

When several messages describing commits on one branch are generated,
they are ordered to one thread.
Use the first email as parent for all subsequent ones
Leave only [] style mailnotications
Call ciabot from gnome-post-receive-email

The mailnotfication script has been removed, so ciabot has to be called
here.
Fix encoding in emails

Make sure that input and output are open with the same encodings.
Do not send emails about auto/* tags
License
Add possibility to define Reply-To address
Rewrite setdescription.sh using git-diff-tree

This the description file is updated only when the spec file was really
changed. It will enable to include in the same loop the updating of
SPECS directory.
Make snapshot of all specs on master branches
Cron job to commit changes to SPECS repo
Hook to push changes to github mirror
tr + - in repository names for github

For some reason github doesn't like + in the name of repository.
Therefore it has to be translated to some other character.