Move geodan/gost to gost organisation

[bertt]

Now all other gost repositories are moved to gost organisation, its time to move this geodan/gost repository also.

Some work todo:

• rename all package references, for example: github.com/geodan/gost/sensorthings/models to github.com/gost/server/sensorthings/models? this implies we'll have a gost/server repository
• fix build servers
• fix links in documents

[bertt]

done