Combined processor trees into one main tree

All processors now add the processor branches to a top-level tree
contained inside DetectorDriver. This tree is named "Pixie16". Processors
no longer contain their own local tree. They still contain a pointer to
their own TBranch.

The detector driver TTree is only filled when there is at least one
processor with a valid event. The total number of filled events is
tracked by det driver. Each processor tracks the total number of valid
events which it contains. This number is printed out upon closing.
Small fix for root output from BetaProcessor
Root data structure changes

I included ROOT dictionary generation in the Makefile. This should make
it easier to extract the data from the ROOT file in the future. It should
also make the filling of the tree more stable and less susceptible to
differences in computer architecture.

I also completely re-wrote the Makefile in order to make it slightly
more readable and to add the dictionary generation. At this time, you
need to add the path ./dict/ to the LD_LIBRARY_PATH in order for
the executable to find the shared library file.
Small fix for TBranch definitions