Add BGPProperties validator as a JUnit test.

To use it, set BGP_PROPERTIES_PATH to your properties file,
remove @Ignore annotation in the test,
and run the test.

If the test fails, a surefire-report will be generated with information of the error.
Debugging may also help to finding where the error is.

The validator can also be run as an application, passing it the path of the file to validate.