jKiler

I've decided I'll give it a try but as long as fixing `ValueByDiscriminator` seems pretty straightforward, it requires some more changes to support proper generation of `FromX` and `MergeX` methods....

This PR adds support for clients to use custom query parameter names. This change is motivated by a [discussion](https://stackoverflow.com/questions/11490326/is-array-syntax-using-square-brackets-in-url-query-strings-valid) on stack how different languages handle array syntax with square brackets...