Bug fixing in FastPrimaryVertex

By Martin:

Two bugs:

1) the fillDescription method ends with the wrong call:
  descriptions.addDefault(desc);
while it should be something like:
  descriptions.add("jetVertexChecker,desc);

2) With a fillDescriptions method, you no longer need
an explicit cfi file in the ../python directory.
Hence, remove ../python/jetVertexChecker_cfi.py.
(This is the file currently used by ConfDB parsing).


The previous fillDescriptions, using addDefaults
more or less implemented the comment a few lines higher:
```
//The following says we do not know what parameters are allowed so do no validation
// Please change this to state exactly what you do use, even if it is no parameters
```
So I guess the comment should also be removed, as now you know exactly what
parameters you want/allow....