Support custom fields in remote db access

[joedolson]

Currently, custom fields are fetched on demand, which means that they are dependent on existing in the local site - they don't use the remote DB connection to get information.

I think the best solution to this is to fetch custom fields when building the event object, so that they're passed to remote handlers. This will also enable them to be more readily available in exporters and the REST API.

[joedolson]

See support request HS7466.