Filter: update the NEDPosition properly

This was storing the data before it was computed.
CFNav: make sure to zero the updated flags

This was causing the filter to run before all information
was available.
CFNav: more init fixes and added error before

Not initializing the history_idx led to writing to random
memory. Also now when the attitude module is not initialized
an error is set.
CFNav: use init baro sample to zero altitude

Since this filter is not using the altitude from the
GPS we want to define the "home" altitude as the value
seen during initialization.
SE(3): do not allow updates with bad positions

Previously getNED did not verify that the home location was
set before performing an update.