forked from SoDOff-Project/sodoff

* DB schema improvements - add column DragonId to table PairData - add foreign keys for table PairData - remove unused column InventoryId from Vikings table - simplifying relations viking -> selected dragon - remove SelectedViking and SelectedVikingId from Dragon - remove column SelectedVikingId from Dragons table - cleanup and arrangement code in DBContext.cs * support for dragons PairData in KeyValueService and in "pairs" API endpoints