Incremental Search of names in Show/Hide Elements Dialog

[roper79]

[JanBliznicenko]

When you start typing in the window, it will actually search, but the search is very basic for now. The limitations are:

• The search field is hidden until you start typing in the window
• It does not filter out selected items, just jumps to first occurence and highlights the rest
• You cannot jump between occurences

Until today's nightly, there used to be the issue that you even had to click into the tree itself first. It is not needed anymore and just have the Show/Hide window focused is enough