- add new <update-interval-secs> for autopilot components.
This does what it says.
- add new method to PeriodicalValue to normalize symmetric around zero
- move the DigitalFilterImplementation out of the header file
- refactor NoiseSpikeFilter: spare some cpu-cycles and respect periodical
output
Split the former single-file-implementation in xmlauto.?xx into multiple
files and use some OO techniques. Started with documentation to be used
with doxygen.