Central attraction coefficient should not be an available parameter in TLEPropagatorBuilder
Calling the method
```
new
TLEPropagatorBuilder(...).getPropagationParameterDrivers().getDrivers()
```
currently returns two parameter drives: one for BSTAR and one for the central attraction coefficient. The TLE theory specifies GM so it should not be available as a parameter.
(from redmine: issue id 313, created on 2017-02-17, closed on 2017-07-27)