Allow multiple keyboard shortcuts per function

[xeruf]

Currently I can assign only one shortcut to any function, which is very unusual - be it vim, emacs, intellij - whatever I work with supports multiple shortcuts per function which makes it easier to stay in the flow in different modes and usage styles.

[stoecker]

We already now have the problem, that we don't have enough shortcuts for the functions we have. We wont increase that problem by allowing to add multiple shortcuts.