Allow app.json without templateType key
Allow app.json without templateType key

The v2 app.json should not have a templateType key in it. MeshInteraction
does require that it is constructed with that key, at least until we
refactor it, so pass a blank string when the app.json does not contain
a templateType key.

https://phabricator.endlessm.com/T11064

endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib