begin moving turtle specific code from opus into turtle package

turtle/autorun/gps.lua

@@ -0,0 +1,43 @@
+local modem  = _G.device.wireless_modem
+local turtle = _G.turtle
+
+if turtle and modem then
+	local s, m = turtle.run(function()
+
+		_G.requireInjector(_ENV)
+
+		local Config = require('config')
+		local config = {
+			destructive = false,
+		}
+		Config.load('gps', config)
+
+		if config.home then
+
+			local s = turtle.enableGPS(2)
+			if not s then
+				s = turtle.enableGPS(2)
+			end
+			if not s and config.destructive then
+				turtle.set({ attackPolicy = 'attack', digPolicy = 'turtleSafe' })
+				s = turtle.enableGPS(2)
+			end
+
+			if not s then
+				error('Unable to get GPS position')
+			end
+
+			if config.destructive then
+				turtle.set({ attackPolicy = 'attack', digPolicy = 'turtleSafe' })
+			end
+
+			if not turtle.pathfind(config.home) then
+				error('Failed to return home')
+			end
+		end
+	end)
+
+	if not s and m then
+		error(m)
+	end
+end