Project Filter merged

[David Nolden]

I don't like that the filter-line is visible all the time. It adds
permanent UI clutter.

What are the usecases of this filter? Isn't it solvable on the
project-manager level? I think that is where we need better filtering
capabilities (It should be possible to specify include/exclude
patterns and directories when importing a project).

If the line stays, then it should only become visible when the user
presses a "Filter" toolbutton.

Greetings, David