Cleans up energy-in-tower function

Renames parameters for greater clarity
Removes last 3 shower shape fit parameters

The first is a scaling factor that multiplies the energy, but is always
set to one anyway.

The other 2 are (x, y) offsets which are always set to zero so they
have no role.
Cleans up fit function implementation

Uses clearer, more verbose, variable naming
Renames n-photon fit function

This is more consistent within this class, as well as the
naming in StFmsEventClusterer.
Cleans up 2-photon fit function

Uses clearer, more verbose variable naming
Deletes unused n-photon variable in 2-photon fit

This must be a holdover from older iterations of the code and is no
longer used.
Changes function argument names

This is more consistent with other functions