The image center (or principal point) could be set wrongly if the previous project had a significantly lower resolution, disallowing values for cx,cy such as the correct ones for the next project.

-> load video (and therefore imagesize) first

New procedure for dealing with invalid pet-file:
- save current state before loading new file
- open new file
- throw exception on erroneous value
- catch exception at top level and restore old state
- show error message

- Delete some dead code in CoordItem
- Slightly refactor `paint`-method

- Introduces `ExtrinsicParameters`-Struct
- Extract `ExtrinsicBox` from `Control`

- Move slots to FilterBeforeBox when concerning its elemets
- Fix Tab order of new extracted widgets
- Delete dependency to Control by AutoCalib

- Add test which reads a "default"-pet file and writes it out and then compares them
- Detect differences in reading/writing/overall file format
- fix: ColorMarker read in saturation for value

- Reads in whole intrinsic calibration at once
 -> reads in reprojection error without setting it to NaN later on

- Also add -autoIntrinsic documentation

- Crash due to comparison of cv::Mat with different size
- Append zeros to old model such that it has the same size as the new one

- Move "filter before" GroupBox into own widget
- Move "intrinsic" GroupBox into own widget
- Save intrinsic calibration in struct
- Use said struct as parameter for `CalibFilter`
- Add `setValue`-helper function for loading values into UI respecting min/max
- Move PeTrack-Version from Setter to Constructor of Petrack-object
- Add Unit-Tests

- Fixed boolean expression with inverted button
- Refactored boolean expression for better readability

- updateControlWidget should set new maximum person Nr
- in 3a2030ba wrongfully changed to set current person; revert this change here
- reintroduce updateControlWidget to editTrackPersonComment