Multiple projects support should be added to indicator-bug

We have to somehow limit the total number of entries displayed in the indicator.
So how many projects do we allow to configure and how many bugs will each project show at most?
Also, in what python data structure do we save the dict for each project?
  We can store a list of objects that we have now, in the same file. Or we can store it as a JSON document (that is for possible future stuff :-) )

I think that we can have few possible solutions, using configurable N:

1. Only show the last N bugs from all projects. For example, show [project name] before each bug.

The good: no problems with scalability. The list will always have the same size.
The bad: some projects may have heavy bug traffic, this may change the list too fast. Not easy to differentiate between projects (although different colourisation is possible).

2. Show list of N bugs for each project. For example:

-----
[Project Name]
<list of bugs>
----
[Project Name]
<list of bugs>
----
....

The good: each project bugs are easily distinguished.
The bad: can become usability problem in case of a large number of projects.

3. Show all bugs per project in a side panel. For example:

[Project Name] -> <list of bugs>
[Project Name] -> <list of bugs>
[Project Name] -> <list of bugs>
...

4. Configuration Window

Mockup: http://www.flickr.com/photos/trevi55/6149474983/in/photostream

The good: no real scalability problem unless a really big number of projects is configured.
The bad: requires two actions to see the list of bugs (two mouse movements).

I guess we should discuss these options and decide.