Added the references necessary for jsoncpp to our setup, and our environment creation (for creation of external_src).
Added exit in the event of non-zero return from untarring boost.
Added JSONCPP setup file, as well as its configuration file.
Added helper paths for all env subdirs, and swapped all directory creations in env preparation to use the helper paths rather than literal names.
Fixed symbolic link for non-env installation case.
Removed symlinking to headers. Not necessary for external_src based libraries.
Add our ext2env setup file (skeleton for now), configuration as well as a skeleton for our external_src CMakeLists.txt
Added call to ext2env setup after external lib steps.