autoconf: add test for alternate json-c pkg-config file

In Ubuntu, json-c pkg-config file is installed under
json-c.pc not json.pc. Test for this version as an alternate
during configure.
autoconf: Add test for uuid library

Add test for uuid library pkg-config.
This library is necessary for build, so we
should be checking for it at configure time.
fix references to json.h

On ubuntu the json-c headers install into /usr/include/json-c
not /usr/include/json, so we need to remove all references to
<json/json.h> and flatten them to <json.h>.

The json-c pkgconfig file takes care of adding -I/usr/include/json
or -I/usr/include/json-c as necessary.