build: move Makefile.am into etc
build: move pkg-config, ldconfig files to etc
build: pkgconfig includes zmq, json, lua libs

Tell users of flux-core how to link to these required libraries,
so they don't have to jump through hoops to find the right ones.
build: add in-tree variant of pkg-config file

Aids in building a framework project against uninstalled flux-core.
Merge pull request #74 from garlick/pkgconfig

enhance usefulness of pkgconfig files for framework projects