Added ability to inject additional extensions to monVer from param file.

[joshmcculloch]

This is useful for operatating a REF/ROV as a TIM type device which the M8P is capable of doing.

To test run: roslaunch ublox_gps ublox_device.launch param_file_name:=m8p_timing /ublox/timtm2 topic will be published if a jumper is made between TIMEPULSE and EXTINT.