Split the peak shaving options into a sub-menu, as the main menu
is getting a little crowded now. Import limit option is only
available if the assistant on the Multi is capable. The menu also
reacts correctly to sites running with/without a grid meter,
or where keepBatteriesCharged is set.
gui-v1 commit: 20de39961eb9f0faf24162b4c520f4f9ef290a1f