Touch navigation issues

 * animated pans (kinetic) after pinch: d42236b658323dc92e360012b329e1a13bebc853
 * rotation threshold should be configurable: f9bf1c0b859967c5015ef9e7de1a19b84386ce07
 * pan kinetic should be configurable: 3b74f72c5656c17b2854481d4d8a35212706fa33
 * don't use private `zoom_`function in `TouchRotateAndZoom.handleTouchMove`

Nice to have:
 * compute the real center of rotation (instead of the centroid)
 * rotation kinetic effect
 * scale kinetic effect
 * animate to final resolution after pinch