make keyboard shortcuts help page

[adameat]

Similar to how it is done in Tracker

comments from @astandrik for clarification:
search for editor shortcuts in code and add to common tracker solution

[alexv-smirnov]

I would think that every function must be available in some menu/button, and if so, that's a general approach to show the hotkey combination in the menu item or button hint.

[antonkovalenko]

requires complete set of commands that are accessible via hot key

[antonkovalenko]

#1343

[antonkovalenko]

this issue is for a new page that contains exisstings hot keys and their actions