Shortcuts and context menu configuration

[dhardy]

Standard actions: currently some standard shortcuts like Ctrl+A, ..+X, +C, +V, Ctrl+Z are hard-coded. These are standard for most Linux and Windows systems but incorrect for OSX, and, further, should be configurable.

Custom actions: it should be possible for an app to create custom actions, most likely on widgets, and be able to set up (local) key bindings to these actions.

Global shortcuts: allow creation and configuration of shortcuts which are active globally, targetting custom actions.

Context menus: allow widgets to add actions to their context menu, both standard ones like Undo and custom ones (including sub-menus like spelling suggestions). [Also, implement context menus.]

• platform-specific default shortcuts
• configurable shortcuts
• widget-targetted globally-active shortcuts?
• global shortcuts?
• context menus

[dhardy]

Done:

• Shortcuts: extend, add specific MacOS shortcuts; rename ControlKey → Command #154 makes the default shortcuts platform dependent
• Config read/write support #155 allows shortcut config to be written to / read from a file