Blender Git Loki

3D View: preferences for rotate sensitivity

Added because the current default is too fast
for painting with tablets, see D5385.

Turntable and trackball have different settings because
turn-table uses an angle-per-pixel, where as trackball
values are relative to the view-port size so a scale is used.

The sensitivity is scaled by the pixel size so hi-dpi views don't rotate faster.