Remove function signature does not match other functions

[kingledion]

The remove function signature:

pub async fn remove<T: TypedCouchDocument>(&self, doc: &T) -> bool

does not return a Result like the function signatures for other 'CRUD' operations create, save and upsert.

Remove should be changed (or possibly deprecated and replaced with a new 'delete') to return a CouchResult so that any errors as well as the http status for the db call call can be returned.