Attitude: no longer needs to be called revolution

This is used for all targets except CC so dropping
the prefix.
EKF: remove baro_offset tracking

The GPS wander is a lot more than the baro for the
time periods we are interested in so the simple low
pass filter currently applied isn't a good model.

In the long run trying to run some medium time scale
state estimate to track the GPS altitude bias and that
is centered around zero and a longer time scale bias
for the baro might be a better approach.
EKF: rename constants more explicitly

add "VEL_" into the variables where appropriate, before
only the POS ones were appropriate.
EKF: remove unused methods

Various explicit update type methods that are no longer
used.
EKF: disable GPS vertical position updates

The baro is more reliable, just use that.
Merge pull request #1027 from peabody124/ekf_work

EKF Cleanup