Use path::is_absolute instead of custom code
Space can be used instead of slash in file chooser (⌘T)

This enables full path search.

Closes #893.
Use custom menu item title for key equivalents

The rendering doesn’t mimic the system 100%, for example the key equivalents are not centered on the split between modifiers and the key, nor are F-keys rendered using a smaller font / menu glyph.

On the plus side though, now all keys are rendered. Previously keys shared with other (non bundle) menu items would only be shown for one of the items sharing the key, and some keys would simply not be shown (e.g. ⌃#).

Also, bundle menu items no longer “eclipse” regular menu items, which could previously happen even when the bundle menu item wouldn’t fire (as it was scoped for something else than the current context).

Fixes #894.
Simplify NSMenu subclass

Now that the bundle menu doesn’t register any key equivalents, there is no need to manually go through all but the bundle menu to avoid having the system trigger bundle menu items.