PSReadLineKeyHandlers should be stackable

[ninmonkey]

Maybe this is a big ask, being able to stack and undo Set-PSReadLineKeyHandlers could be quite useful.

Here's a few sample cases that would be nice to be able to toggle them

• WrapParenthesisSelection
• Smart Brackets
• toggle quotes

[StartAutomating]

I'm not sure stacking would be the exact right answer here.

I think that it might be better to expose keymapping in the types files (for instance, by making some scriptmethods).

The unresolved question is where to put them.

It could be part of the overall work with the host #129