Split off VDC efficiency calculation from THaDecData

Start conversion of this code into a physics module named VDCeff
Add VDCeff module to build system and ROOT dictionary
Add Begin() and End() functions (dummies for now)
Implement most of Process(). WriteHist() part still missing.
Implement WriteHist(). Remove trailing whitespace. Reset hist_eff every cycle.

Among other things, the destructor and Init() are still incomplete.
Find the global VDC variables for each plane. Warn if any not found.
Properly set the histogram names. Finish destructor that cleans up histos.

Histogram "names" in the database are expected to be just the name prefixes,
e.g. "Lu1", "Rv2" etc. They will be suffixed with "nhit" and "eff" for
number of hits and efficiency histograms, respectively.
Fix bad typo in Begin(). Efficiency histograms were never created!
Get rid of old, original code that was hanging around as comment blocks
Check name/histname in ReadDatabase and quit if undefined.
Check for duplicate global variable and histogram names when reading database.
Replace Clear() with Reset(). Remove unused DefineVariables().

Reset() zeros all histograms. This allows one to restart the efficiency
calculation at any point without having to reinstantiate the module.
Add example database file for VDCeff module

This database matches the hardcoded setup in the original THaDecData.
Move VDC efficiency calculation into a physics module. (Merge branch 'vdceff').

The Process function of this module is essentially copied from the code
that was previously in THaDecData and should behave exactly like it.

Note that the module requires a database file. A default database,
corresponding to the original configuration, is provided in the DB/DEFAULT
directory. Using the database, the efficiency can now be calculated for
wire spectra contained in arbitrary global variables, and histogram names,
number of wires, number of events between recalculation etc. are configurable.