Enhancement: Provide support for SGP scoring

[dspreitz]

I received a request, if aeroscore would support SGP format scoring from the gliding contest in Hockenheim. In 2019 they will have a 18m class flying in SGP format.
Here is the SGP sporting code.
http://sgpstorage.blob.core.windows.net/sgpmedia/1719705/sgp-rules-v9.0.pdf

[Turbo87]

I probably won't have time to implement it until then, but since it's close to a regular racing task they can probably use that instead until we have support for it