Reverting of the ProjectManagerView filtering patches

[Aleix Pol]

Hi,
I just reverted David's patches that are related to adding some
elements in the project model when the model is being filtered. We all
agreed that the feature is really interesting but we couldn't manage
to get a good implementation.

If anybody wants to give it a try and make a Proxy model that adds
items for the filtered values that would be great, since the feature
is good, but we cannot maintain such a feature.

Aleix