Improve the fep_efficiency.sh

[j-kleemann-old]

Currently the fep_efficiency.sh script is very simple and specific in the choice of the filenames.
We could think about making it a bit more versatile (and more compatible with the utrwrappers typical output filenames) some time in the future.
This could aid users with less technical know-how to get efficiencies from any histogramToTxt output.

For example, instead of multiple parameters one could implement options for controlling the behavior of the script and let all other arguments be the names of files to process.
In such a case simple globing can be used to determine the files to process (e.g. efficiency*det1.txt) and the output would simply be needed to be sorted according to the energies.