input_delete_to_start

[eoli3n]

As seen in #328, there is no function to emulate term C-u
Maybe duplicate of #300 ?

[osa1]

#382 is merged and we now have a input_delete_to_end action. Perhaps we can also implement this. @trevarj do you see any problems with this? It's fine if by default we don't have a binding for it.

[trevarj]

It should be an easy addition. I will have a look later