Single location for entity type list definition

[mrclay]

Currently the mapping of entity types to classnames is hardcoded:
​https://github.com/Elgg/Elgg/blob/1.8/engine/lib/entities.php#L631
​https://github.com/Elgg/Elgg/blob/1.8/engine/lib/entities.php#L964
​https://github.com/Elgg/Elgg/blob/1.8/engine/lib/entities.php#L1552
(and probably more)

While entity types are rarely added (and shouldn't generally be by plugins), I need it for my plugin :)
​https://github.com/mrclay/Elgg-xcollection
I had to fork get_entity(as_row) and delete_entity to workaround this, but I'd have to fork a lot more to support metadata, etc.

In the short run I may have to rewrite this as an ElggObject, though this would add more work porting it back into core later.

[mrclay]

I've recoded my plugin as an ElggObject so I've personally no immediate need for this. Further I don't think it's wise to enable this by plugin devs (e.g. would we have to give devs the ability to alter the entities.type ENUM?); using objects is probably a "good enough" way to model future potential entities.

[cash]

I left a comment on ​http://community.elgg.org/pg/forum/topic/830706/entity-list-spec/

Independent of your work, it makes sense to put all the entity types in a central place.

[Cash Costello]

Fixes #4272 where an array of entity types can be used, use array in config object

Changeset: 5a3390fbb42a787f7c2ba4f13b6a6843d9a90c7b

[Cash Costello]

Fixes #4272 where an array of entity types can be used, use array in config object

Changeset: 5a3390fbb42a787f7c2ba4f13b6a6843d9a90c7b