Fix usage of default track line width setting
Barometic pressure; -hpa to hPa, limit scaling to 930-1100. Also move the base line to 18 from 27.
Merge pull request #92 from stedy6/master

Barometic pressure, hpa to hPa, limit scaling to 930-1100. base line to 18 from 27.
Merge pull request #93 from Ptizef/master

Divers improvements
Correct NMEA MDA sentence checksum calculation.
Correct Dashboard wind speed history logic to use MWD sentence.
Correct wind and baro history graphics for linux systems.
Merge pull request #94 from Ptizef/master

Add the "moving" grib file option  from Saildocs
Improve GRIB Pi memory footprint, correct wind direction arrows in course-up mode.
Change playback time interval setting : only one parameter instead of two
and do not allow values witch are not sub-multiples of the original file
intervall to ovoid inconsistencies . Also make it more understandable
to common users.(#FS 1337)