Correct the interpretation of DetectorDotDatFile

The Number of columns in a detector.dat file is 5 plus the number of user
table parameters. This commit correct this information.

re #8003
Correct the incorrect assumption of detectordotdat file

Although present almost always, according to the control group, the phi
column is the first of the User optional column. So, we can not suppose
it is there.

re #8003