This MR changes the shortcut for jumping to a frame from Alt + DblClick to Ctrl + Alt + DblClick and differentiates between Alt+Click and Ctrl+Alt+Click to resolve issue #328 (closed)

This way, only the jumping, without the changing of the trackpoint, gets activated,

Closes #328 (closed)

Reviewer Checklist

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()