Update the liste of all shortcuts

[Jiri Srba]

Make a table with overview of all shortcuts used by TAPAAL and add this to Menu/Help. If possible, it should be gathered automatically so that when new shortcuts are introduced, they will be automatically detected.

[Kenneth Yrke Jørgensen (yrke)]

We already maintain a list: https://github.com/TAPAAL/TAPAAL/wiki/Shortcut-keys

[Jiri Srba (srba)]

I was wondering, whether the list can be displayed inside of TAPAAL (e.g. in Help menu) so that it is gathered automatically (i.e. adding new shortcut will automatically be added to the list)

[Jiri Srba (srba)]

I think the title "make list ..." was better as such list is not made in the code
(it is only manually maintained on the web). I though that there should be an automatic
way to gather all used shortcuts and display them in the help menu.