Introduce jsoncpp library into project

* This is our phased-in replacement for json_spirit -- yay! I was not
able to successfully get the project linked into nomlib as a static or
dynamic library on OS X, so... inclusion directly was satisfactory evil.
Luckily, jsoncpp came well prepared for that situation!

* See comments made in the cmake scripts for further insight...
Merge branch 'feature/jeff/jsoncpp' into dev