build: move library related code to lib/

Cleanup main Makefile and remove all library related code to
lib/ to better support the increasing number of libraries and
to keep the main Makefile clean from library dependencies.

Jira: ZEP-308
Change-Id: Id83cf309020604b8eab8d80cad0021905d5b5f7a
Signed-off-by: Anas Nashif <anas.nashif@intel.com>