256 subscriptions are enough for now.
Reduces RAM usage by 300 bytes.

Not used yet, it should not affect anything, except for slight RAM
increase.

Previously the formats of all known uorb messages were written.

- reduces header size by about 13KB
- reduce ulog_message_format_s size to reduce required stack size.
  Largest message format is about 1000 bytes.

Previously the acceptance radius was 0, so the FlightTaskAutoLine was
randomly changing yaw and sometimes going into a random direction.
There is still something else wrong in there, but avoids the reposition
problem.

If the filter was disabled, the apply() would always return 0.

in order to not constantly switch mag fusion mode in gusty winds.