Add general settings to React editor

Some of the settings from the GWT editor are appropriate for the new React editor. Some of them should be moved to an advanced settings dialog so they are not so prominent.

• Editor buttons: do not reimplement.

• Enter key saves immediately: ???

• Syntax highlighting: not yet present

• Show save as approved warning: no longer relevant

• Navigation options: no longer relevant

• TM options: not relevant (now a toggle on the panel) - should persist this.

• Page counts: option should be next to the paging buttons (ZNTA-2085)

• Display config: do not include in the settings panel (controlled by buttons on the panels now)

Persist some options to local storage:

• suggestions diff setting

• which panels are open