UV coords are scaled by aspects (see UVsToTransData). This also applies
for the Cursor in the UV Editor which also means that for display and
when the cursor coords are flushed (new 'recalcData_cursor_image' was
added for this), these need to be converted each time.
This flags moving the cursor in the Image Editor T_2D_EDIT with the
following benefits:
- dissallowing e.g. Z constraints
- improving the header display
- it should not use scene units
- now respects if we are moving in pixel coords or not