create-Qt-pushbuttons

[jpka-]

This commit supersedes my commit #1969.

1. Three types of knobs (internal, calf, openav) redrawn with Qt only; no substrate svg/png image need now. Now hover enlighting works on all knobs. All is vectorized and use HSL color model. This is a complete work, intended to be replacement of current scalabledial.py file, tested also by CPU usage.
2. But it is one way ticket: png/svg stuff removed.
3. Three types of 2- and 3-positions pushbuttons created. The idea is to make buttons well different from knobs, while still keep skin style, include disabled items. Used now for booleans, and integers @ [0,1], [0,1,2] ranges.
4. Mouse wheel captured for QDial, it solves #11 and gives exact control for bools/ints, while smooth one for floats. Use with Ctrl or Shift also.
5. Left mouse button toggles pushbuttons.
6. Hotkeys introduced when mouse hover active (no mouse press need) for both pushbuttons and knobs: 0...9 to set absolute value; Home, End, PgUp, PgDn. Note: 'Home' interferes with Canvas control hotkey.

Hope it will be useful.

[jpka-]

Please see updated #1971 which should include this code.

[falkTX]

Moved to #2010