Revert catkin warnings to fix regressions (problems with catkin -lpthreads errors)

For reference and reasons, please check:
https://discourse.ros.org/t/need-to-sync-new-release-of-rqt-topic-indigo-jade-kinetic/1410/4

* Revert "Fix gazebo catkin warning, cleanup CMakeLists (#537)"
This reverts commit 5a0305fcb97864b66bc2e587fc0564435b4f2034.

* Revert "Fix gazebo and sdformat catkin warnings"
This reverts commit 11f95d25dcd32faccd2401d45c722f7794c7542c.