Robust, device-friendly unlock. Added gitsubmodule for unlock_apk.
reset.sh now builds the apk. adbs unlockScreen method now invokes
unlock.apk. added a new small, focused module called device_state to handle determining state of emulators/devices. currently has a "isScreenLocked" function. unlockScreen in adb.js now 1) checks if screen is locked or not first before doing anything and 2) uses unlock.apk to do the unlocking.