Add 'calc', 'fuel_gauge' and 'fuel_level'

[stephenholleran]

From the floating lidar file format discussion #268 it was decided:

1. To sensor_type add:
   1. calc (Discussion #268)
   2. fuel_gauge (Discussion #268)
2. To measurement_type add:
   1. fuel_level (Discussion #268)

This can be reviewed now but probably shouldn't be merged until the floating lidar work is completed.

[kersting]

It is all good.