Feature/30 enums

[clbarnes]

resolves #30

[clbarnes]

To check:

• Are relation IDs (those built into mainline CATMAID, anyway) always the same? The connector_types endpoint always fetches them from the database, so maybe not. But some endpoints are documented in a way which suggests that they are.

[aschampion]

I think we want to not assume relation IDs are always the same and can be project-defined. Endpoint docs are legacy and should be updated. Relation IDs should be fetched and cached once per-project.

[clbarnes]

Rebased on master after #27

[clbarnes]

I think we want to not assume relation IDs are always the same and can be project-defined. Endpoint docs are legacy and should be updated. Relation IDs should be fetched and cached once per-project.

Makes sense. In that case, I guess it'd be better to define the enum using the string representations here https://github.com/catmaid/CATMAID/blob/master/django/applications/catmaid/control/connector.py#L35 , and then make a method/function which returns a list of (relation_id, relation_name) tuples, so that users can do the mapping both ways.

The enum could be scrapped entirely if we're treating the relations as dynamic, but that doesn't quite feel right either.

[clbarnes]

Rebased on master after #28

[clbarnes]

@aschampion done. Adds some complexity but I think it's the best way to do it while still keeping the nice bits of enums.

It'll break when different connector types are added but catpy was always going to be brittle to changes in CATMAID.