[IDEA] Use RapidJSON's jsonschema implementation during filters' conf load

[frikilax]

What is your feature about ?
The jsonschema specification will be used in the manager in v1.2.
The RapidJSON library included in the filters' code is also able (in a simpler way) to perform json validation.
The idea is to use these validation capabilities to verify filters' configuration at runtime.

Describe what you'd like
The validation should especially include fields type validation, requirements and control over additional fields.

Additional context
Refer to jsonschema for a reference to this schema (WARNING: RapidJSON implementation is Draft4)