add switch to master script

scripts/switch_to_master.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/bash
+
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null && pwd )"
+cd $DIR/..
+
+git clean -xdf .
+git rm -r --cached .
+
+git config remote.origin.fetch "+refs/heads/*:refs/remotes/origin/*"
+git fetch origin master
+git checkout master
+git reset --hard
+git submodule update --init
+
+printf '\n\n'
+echo "master checked out. reboot to start building openpilot master"