metadata_key_validate
Description:
Validates value content complies with the key specification.
That is, it has the expected type, and value are within the range specified in key (for integer values).
Parameters:
| this | 
           the registry instance  | 
      
| key | 
           a metadata key  | 
      
| value | 
           value to be validate  | 
      
Returns:
| 
           true if complies  |