SanityCheck: do not allow flying autonomously in indoor mode

This configuration is unsafe since position will always read
zeros.
SanityCheck: make this compile on COPTERCONTROL
SanityCheck: do not allow navigation in "raw" filter

In principle this can be done. In practice, it doesn't verify the
quality of the GPS lock and hasn't been tested, so should be
disabled by default.
Attitude: add NONE navigation filter

We previously tried to use a RAW mode for the GPS to pass directly
for navigation, but this could also be confounded with situations
when you didn't want GPS. This created an ambiguous situation and
prevented us performing sufficient safety checks.

Now the user either expressly selects "NONE" for no navigation, and
if they attempt it there is an error.

If they select RAW and there is no valid GPS signal, it will also
set an error.
Attitude: handle NOHOME case for setting errors
Attitude: in RAW mode, make sure queues are flushed

This prevents event system warnings when there is no home location
set.
Merge pull request #1151 from peabody124/insindoor_sanity

SanityCheck: do not allow flying autonomously in indoor mode