Add rudimentary version of cut/copy/paste to the menu

The names default to the action names and there are not keybindings.

See #1.
Add custom names/shortcuts to cut/copy/paste and select all

The text components now behave more sanely since they all react to the
usual keyboard shortcuts for cut/copy/paste/select.

There might still be a groovier way of doing this.

See #1.