refactor(gen:endpoint): configurable route url

* Configurable route base, defaults to `/api/`. This only affects the
  client URL, the backend code will still be written to `server/api`.

* Configurable pluralization of route, defaults to true.

Closes #338
Merge pull request #350 from mvhenderson/feature/configRouteUrl

refactor(gen:endpoint): configurable route url
fix(app:server:thing.controller): missing `res` param for handleError added