select/focus on the first input-field when opening the track-properties-window

[Stephan Huebner]

One thing that is totally counter-intuitive to me is that when I open the window to edit track-properties I first have to click into one of the fields to actually do that. As this is most probably the main reason why I opened the window in the first place, it would be nice if the first input-field would be selected/focused automatically, so that the cursor is placed in it. This way I could either just start typing or I could use "Tab" to jump to the field I want to edit. Which both is probably faster than using the mouse to activate one of the input-fields manually.

[Mathias Brodala (mathbr)]

Fixed with r4124.