last_checksum_wrong is always FALSE. And probably a bad idea anyway.
[modules] nav_survey_poly_osam: sweep improvements

Added half U-turn even if not sweepback
Some modification to change sweep distance and number of points using telemetry parametrers
option to use default 1/2 sweep distance for start line or using alternative 1/32 sweep start

Its is very useful when using poligon survey osam for photogrametry

closes #938
[conf] update settings_modules in confs
[modules] fix poly osam

variable initialzation only in own block
[modules] digital_cam also for jsbsim
[modules] nav_survey_poly_osam: protect dc stuff
Merge branch 'master' of https://github.com/paparazzi/paparazzi