Add common parameter handling

Add common parameter handling

This common module is proposed to handle all parameters and properties
for the ONAP Policy Framework in a common way.

Parameters and Properties:
- are validated once when they are loaded and need not be checked again
  in classes that use them
- are available for lookup in a parameter service, they need not be passed
  in constructors and method arguments
- are input using a single implementiation of input method only
  (JSON/YAML/Java properties/REST)
- are defined in a schema and the schema is used for validation as much
  as possible

Issue-ID: POLICY-922
Change-Id: I1fac88b9e952b6b5fcbea04319cb4294a9653327
Signed-off-by: liamfallon <liam.fallon@ericsson.com>