Add DataWriter interface to be implemented  by classes that convert LCIO collections to DST data (HpsEvents)
Add EventBuilder interface to be implemented  by classes that use LCIO collections to build HpsEvents
SVT implementation of DataWriter used to convert LCIO track and hit collections to DST data
Implementation of EventBuilder used to convert data from the Full HPS run to HpsEvents
Various utilities used to extract information from LCIO tracks
Update CMakeLists to reflect addition of dst and utils classes
Executable used to create DSTs for the HPS Experiment from LCSim recon files