Changes 2-photon fit arguments to arrays

This enforces the fixed number of parameters (7), which isn't the case
with vector. It is also more self-documenting.

As a result the setMinuitParameter() method is made a template method so
the same code can be used with vector and array arguments (for n- and
2-photon fits respectively).

std::array has to be hidden from CINT, as CINT can't deal with C++11.
Removes error fields from fitted photon

These are not used for anything any more in the code, if they ever were.

The error calculations for the 2-photon fit are also quite complicated
to look at, so it seems simpler to remove them for that reason also.
Removes Clear method from fitted photon
Moves constructor implementation to header
Deletes unused source file
Simplifies field naming
Changes float fields to double
Deletes unneeded ClassDef

No longer needs to include Rtypes.h