Get back to file nuts and bolts now that we have a clearer idea of how things will work.  Changes:
 * The input file will always be read-only
 * The input file may be in two types, one of which is "raw" and comes from alcapana
 * Define the names of branches and such in a file format.h. This acts as a central record of globally meaningful values (e.g. the raw data is on a tree "EventTree")
Small changes to coments i forgot
Minor changes to unit tests
Slight formating change to make DEBUG_VALUE easier to read.
Now iterates over input.
Change how macros are handled in doxygened output.
Put the definitions in an implementation file (sort of**).  Could have used an unnamed namespace, but this results in only one copy of each constant in the static store.

**If you're looking at this commit wondering what's going on: actually i used some macro silliness so that the header expresion becomes a set of definitons when included in the cpp file.  Nothing to see here, move along.
We can now save branches to the output file for each element of TGlobalData. Filling them is another matter, but it's a start.