* Added missing resource strings for new SSH bindings
Without these the settings page has no labels for these bindings.
* Rationalise default SSH keybindings
The logic is:
- Adhoc SSH tabs and windows are based around the Y key
- SSH profile tabs and windows are based around the U key (next to Y and
easier to reach than Z)
* Reorder command enum
Group commands together in a more logical order. In particular, this
makes command keybindings appear in a more logical order on the relevant
Settings page.
Note: this does not break existing keybinding configuration.