[Qgis-developer] Plugin installer 1.0 :)

[Borys Jurgiel]

Hi (mainly Tim),

I've cleaned and refactored the Plugin Installer and finally set the version to 
1.0 :)

First of all, there were some small issues in case a few instances/versions of 
the same plugin was available (e.g. an official, an unofficial, and a testing-
experimental). Now it should always properly choose the best allowed version.

There is a question now, are we putting it to 1.1?

A big part of the code was refactored, but I've tested it on Ubuntu and WinXP, 
and no problems have occured in the most murderous situations I've prepared. 
I didn't test it on Vista, however.

I didn't implement any new features except one small warning message (displayed 
during QGIS startup in case the Installer detects that there is an obsolete 
plugin installed in the home location and it masks a newer version, shipped with 
the current QGIS installation).