[cygnus-ngsi][NGSINameMappingsInterceptor] Allow regular expression replacement for EntityIds

[dmartinezgomez]

The current behavior is that only RegEx Matching is allowed with a constant replacement.
It will be nice to allow the use of reular expressions also in replacement.

E.g.
Entities like: "Air_0001","Air_0002","Air_0003","Air_0004",...
should be mapped like: "AirQualityObserved0001",...

{
  "serviceMappings": [{
    "originalService": "service",
    "newService": "new_service",
    "servicePathMappings": [{
      "originalServicePath": "/subservice",
      "newServicePath": "/new_subservice",
      "entityMappings": [{
        "originalEntityType": "entity_type",
        "originalEntityId": "(Air_)([0-9]*)",
        "newEntityId": "AirQualityObserved$2",
        "attributeMappings": []
      }]
    }]
  }]
}

[fgalan]

Implemented by PR #1457