Fix TypeError exception in db.py on add activities

Fix TypeError exception: tuple indices must be integers, not str.
Do not create new connection for each notification

This typo caused creation of new dbus connection every time a
notification was sent.
renamed function for storing tag autocomplete preferences
fixes #80
Merge pull request #121 from sebastian-leidig/master

corrected function name: set_tags_autocomplete -> update_autocomplete_tags
Merge pull request #119 from tbabej/Fix_typo_bug

Typo notification_conn -> _notification_conn : Do not create new connection for each notification
Merge pull request #112 from msize/patch-2

Fix TypeError exception in db.py on add activities
Fix the bug occurs during addition of activity

Bug occurs after entering '@' sign.
Fix the bug while changing category of an activity

More:
https://github.com/gsobczyk/hamster/issues/15
Merge remote-tracking branch 'projecthamster/master'