Merge pull request #346 from linas/master

Remove old C++ REST API (replaced by python/web)
restore json_spirit usage

Oops .. who knew that there was a hidden dependency here?
build json_spirit, as well.
re-order the order in which directories are built
blow away trails, tehy're unusued.

They're unused by anything except old C++ PLN code.
New PLN code will use TrailLink objects to store trails.