Merge pull request #25 from brash99/develop

Update SCons compilation instructions in README.md, and improve 'scons -c' procedure.
Modified THcAerogel::ReadDatabase
1) Need to add fNelem to DBRequest to read parameter arrays.
2) Added optional variable and set to true. Flag in the
DBRequest to tell code that parameter is optional
and does not have to be found.
3) Move setting of fNelem to before DBRequest for aero_num_pairs
 so that it can be overwritten by parameter file.
Merge pull request #26 from MarkKJones/mkj

Modified THcAerogel::ReadDatabase
Latest version of podd Release-150.
Address some minor issues reported by cppcheck

These were related to a) scope of some variable declarations, and b) use
of pre-increment vs. post-increment of non-primitive types (this has a
slight performance hit due to the way that pre- vs. post-increment
operators are overloaded in C++.

Also cleaned up a few places where initialized variables were not being
used.
Merge remote-tracking branch 'upstream/develop' into develop