[Ticket: #668]

Also implemented a new weight counting for tags.

In addition, the dialogue for managing the theme cloud was improved,
as the old format of the comment data was used there and bugs occurred.

[Ticket: #638][Ticket: #639]

[Ticket: #636][Ticket: #633]

[Ticket: #626]

A number of bugs have been reported,
some of which this commit should fix.

[Ticket: #617][Ticket: #620][Ticket: #621]
[Ticket: #622]