Reorganize directory structure to add common, move docs

[jackguo380]

kk so I updated the cartographer script to be more general and called it setup_third_party_build.sh. This build now also includes opencv so we don't have a repeat of these disastrous build errors. The use case is still the same but the suggested directory name is now:

./setup_third_party_build.sh propbot_3pp_ws
cd propbot_3pp_ws
catkin build
cd ..
#
# Build Propbot
cd propbot_ws
catkin config --extend ../propbot_3pp_ws/devel
catkin build
cd ..

Since the build is so excessively long (20+ mins easily), I split it up into two different builds depending on the use case:

Autonomy

cd propbot_3pp_ws
catkin build propbot_3pp_autonomy
cd ..

This just builds cartographer for use in propbot_autonomy

Mapviz

cd propbot_3pp_ws
catkin build propbot_3pp_mapviz
cd ..

This just builds opencv and some SWRI packages for mapviz. (No cartographer)