Add missing variables to HK setup function. This now allows HK to be set up without first setting up a cylindrical WC.  Resolves #14.
Cosmetic rearrangement of some of the functions in WCSimDetectorConstruction class.  Moved all the configuraiton functions, SK, HK, and LBNE WC to their own file (WCSimDetectorConfigs.cc).  Also moved the PMT QE code to its own file (WCSimPMTQE.cc).  Now ConstructWC.cc and ConstructHK.cc only contain the functions necessary to construct those geometries.

This change is purely cosmetic and changes no functionality since all these source files correspond to the same class.
Added a note saying that this little utility function should be called in all HK configurations.
Add documentation to the top of all 4 of the rearranged files.
Moving the documentation.
Merge pull request #15 from WCSim/feature/issue14

Feature/issue14