(ORG-8511)
Support 3 panning mode.
- Pan by percent: Default behavior. Every time +/-/Left/Right key is pressed using mouse wheel to scroll once will pan by percent.
- Pan by major ticks: Every time +/-/Left/Right key is pressed using mouse wheel to scroll once will pan to next/previous major ticks.
- Pan by minor ticks: Every time +/-/Left/Right key is pressed using mouse wheel to scroll once will pan to next/previous minor ticks.
After user clicks button to go into Zoom and Panning mode, or holds down X key to go into Panning mode, user can press SPACE keyboard to toggle panning modes.