DM-1603: Fix qserv build to use eups version of SWIG

- Introduced SWIG binary variable so qserv scons scripts would pick
up the setup eups version of the swig preprocessor instead of using
whatever happened to be around in the external environemnt.

- SWIG 3.0.2 compatibility: forward declared nested class
TransactionSpec::Reader was tripping up swig with a swigregister
name collision.  %ignore'd TransactionSpec::Reader to workaround.

- SWIG 3.0.2 compatibility: needed to cut over from old SWIG_SHARED_
POINTER macros to the newer %shared_ptr facility.  Some %include
reordering was also necessary in czarLib.i, since swig's implicit
conversion of shared pointers (derived* to base*) does not work
correctly with partial/forward type declarations.