Add option to share to Loop just once every 5 minutes

[paulplant]

• option added to the developer settings to limit sharing BG array to just once every 5 minutes (should maybe move all Loop options to a separate section in the future)
• added as a Loop 3 has removed the check to only calculate Loop cycles every 5 minutes and with the 60 second CGM data from Libre 2 BLE, this causes loop cycles very often and maybe drain some pump batteries.
• note that this new option does not give 5 minute readings per se... it will give Loop the array of last readings (irrespective of if they were every 1 or 5 minutes) every 5 minutes. The user will still see readings every 60 seconds, but they will arrive in blocks every 5 minutes and trigger a Loop cycle.