Query derived types

[kbarbounakis]

Is your feature request related to a problem? Please describe.
Support of querying derived types

Describe the solution you'd like
serviceRouter should implement OfType(DerivedType) route parameter e.g. /api/Actions/OfType('UpdateAction')

Additional context
https://www.odata.org/blog/enhancing-odata-support-for-querying-derived-types/
http://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#sec_PathExpressions