[fpc-pascal] Parameter Checking in fpjsonrpc

[Simon Ameis]

> It is mising, but not forgotten; I have it on my todo list still,
> together
> with some other items for JSON-RPC
> If you feel like implementing some rudimentary checks, please feel free.

Let me see, what I can do next week.

At least some checks if a parameter object has the required parameters
should be doable.

Maybe you could give me some hints on details:
- How should an array correspond to ParamDef? Ignore, trigger exception,
if array of objects, check parameters on each object?
- What to do on additional parameters of an object? Silently ignore them
or shall they raise an exception?

Simon