Imposed root file size limit

DetectorDriver now automatically opens a new root file when the current
one reaches roughly 2 GB in size. The naming convention is...

 - filename.root filename_01.root ... filename_xx.root

Created makefile directive to create the obj directory.

Changed the virtual methods Process and PreProcess in EventProcessor
to return only false if they are not overwritten by a sub-class. Removed
PreProcess from LiquidProcessor because it did nothing. Processors no
longer call the virtual methods Process and PreProcess inside EventProcessor.
They now check the initDone flag directly. Process and PreProcess will now
return true only if data has been filled into the root variable branches and
false otherwise. Now we will know that there is at least one valid processor
entry before filling the tree. This should cut the total number of tree
entries by a signifcant amount.

Changed DetectorDriver to fill the tree ONLY when at least one of the
PreProcessors or Processors returns true. This also required changing the
processors as well. They now only return true if there is valid data to
fill into the root tree.