Remove connection and client subclasses of Link and put the connection
logic into a "connector" class. The connector deals with sending
and receiving messages, handling the connection and reconnection of lost
connections and giving sequence numbers to messages.
This move the logic of the actual connection away from the link
sub-classes, which in turn means the connection should be a lot easier
to mock in tests.
Move item database, tests, endpoint definitions for /api/place,
/api/remove, /api/inventory, /api/inventoryAsObject, and the web
interface view for the storage page into the clusterioMod plugin.
Hornwitser