Add sherpa2 activity models
Add initial synchronization and conversion methods
Add sherpa2_id field for imported aktiviteter
Implement initial sync/convert methods outline
Convert publication date
Convert foreninger
Define main and co_foreninger based on type
Convert code field
Convert title field
Reorder
Don't pass instance variable to instance method
Convert ingress and content fields
Convert lat/lon fields
Convert counties field
Convert locations field
Convert difficulty
Convert audiences
Remove 'trip' category
Convert categories
Save object before updating relational fields