Reorganize keybinding dialog

• Create new dialog class for keybindings
• Group keybindings and show them grouped in the new dialog
• only mention near trackpoint if key part of the functionality
• add compile_defintion for OS to petrack_core as well to enable nice shortcut formatting

Current proposal:

Closes #446 (closed)

Reviewer Checklist

Formatting

• the pre-build checks succeed

General code quality

• naming conventions are met (see .clang-tidy for detailed information)
• no static analyzer warnings in new code parts (e.g., use clang-tidy for checking)

General usability

• old versions of pet-files are still loadable

Only if changes in UI

• new elements are also saved and loaded from pet-file
• check if tab order is still correct
• all new SpinBoxes are promoted
• new keybindings added to Petrack::keyBindings()