Better GPS power management options

for https://github.com/meshtastic/Meshtastic-device/issues/376

mesh.proto

@@ -481,6 +481,45 @@ enum RegionCode {
   // Add new regions here
 }
 
+/**
+  How the GPS hardware in this unit is operated.
+
+  Note: This is independent of how our location is shared with other devices.  For that see LocationSharing
+**/
+enum GpsOperation {
+  // This is treated as GpsOpMobileSlow - it is the default settting
+  GpsOpUnset = 0;
+
+  // This node is mostly stationary, we should try to get location only once per day,
+  // Once we have that position we should turn the GPS to sleep mode
+  // This is the recommendated configuration for stationary 'router' nodes
+  GpsOpStationary = 1;
+
+  // This node is mobile and we should get GPS position at a rate governed by gps_update_rate
+  GpsOpMobile = 2;
+
+  // We should only use the GPS to get time (no location data should be acquired/stored)
+  // Once we have that position we should turn the GPS to sleep mode
+  GpsOpTimeOnly = 3;
+
+  // GPS is always turned off - this mode is not recommended - use GpsOpTimeOnly instead
+  GpsOpDisabled = 4;
+}
+
+/** 
+  How our location is shared with other nodes (or the local phone)
+**/
+enum LocationSharing {
+  // This is the default and treated as LocEnabled)
+  LocUnset = 0;
+
+  // We are sharing our location
+  LocEnabled = 1;
+
+  // We are not sharing our location
+  LocDisabled = 2;
+}
+
 // The entire set of user settable/readable settings for our radio device.
 // Includes both the current channel settings and any preferences the user has
 // set for behavior of their node
@@ -521,6 +560,20 @@ message RadioConfig {
     /// The region code for my radio (US, CN, EU433, etc...)
     RegionCode region = 15;
 
+    LocationSharing location_share = 32;
+    GpsOperation gps_operation = 33;
+
+    /// How often should we try to get GPS position (in seconds) when we are in GpsOpMobile mode?
+    /// or zero for the default of once every 30 seconds
+    uint32 gps_update_rate = 34;
+
+    /** How long should we try to get our position during each gps_update_rate attempt?  (in seconds)
+    Or if zero, use the default of 30 seconds.
+    If we don't get a new gps fix in that time, the gps will be put into sleep until  the next gps_update_rate
+    window. 
+    */
+    uint32 gps_attempt_time = 36;
+
     /**
     This setting is never saved to disk, but if set, all device settings will be
     returned to factory defaults.  (Region, serial number etc... will be