General bug fixes and UI changes

Bug fixes:
- Fixed tracking LOAD button seg fault.
- Fixed internal target flipping of 180 degrees.
- Fixed track image not being produced from post-process tab.
- Chessboard calibration circles now show on Linux.
- NCC range changed from 0...1 -> -1...1.
- Max rate now 999ms.

UI changes:
- Moved Camera Calibration from toolbox to tab view.
- Moved Position Calibration from toolbox to tab view.
- Disabled videoposition bar when not needed i.e. rate changing.
- Moved milliseconds (ms) suffix to label in Tracking Tool.
- Changed wording on Print Default Grid button.
- Default square size now 10cm in Camera Calibration.
- Minor UI changes.

Other:
- Update to travis.yml.
- Updated README.
- Updated CONTRIBUTION.