Throw error if .find has payload type and EntityFactory mismatch

[MichaelHirn]

Example:

Assume CID 0x123 responds to payload { type: 'DataProperty', ...}.

The proposed behavior for .find('0x123') is:

client.Entity.find('0x123'); // does not throw, returns `entity instanceof Rlay_Entity`
client.DataProperty.find('0x123'); // does not throw, returns `entity instanceof Rlay_DataProperty`
client.Individual.find('0x123'); // does throw; error message: expected payload to be of type 'Individual' but got 'DataProperty'. Call client.DataProperty.find.
client.{X != DataProperty || Entity}.find('0x123'); // does throw; same as client.Individual.find

The point of this is, that you can assert a specific Entity type when using find.

If you want to fetch it without knowing the type of the entity one should call client.Entity.find