install pip dependencies using local virtualenv, also support install target

[k-okada]

this will install pip dependency to package-local virtual env, i.e. share/${PACKAGE_NAME}/catkin_env

to test this code, make workspace with this PR and test code (https://github.com/k-okada/gdown) use catkin_make or catkin_make install

install$ rosrun gdown python2
Python 2.7.12 (default, Nov 20 2017, 18:23:56) 
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import ez
>>> ez
<module 'ez' from '/home/k-okada/catkin_ws/ws_catkin_pip/install/share/gdown/catkin_pip_env/lib/python2.7/site-packages/ez/__init__.pyc'>
>>> import gdown
>>> gdown
<module 'gdown' from '/home/k-okada/catkin_ws/ws_catkin_pip/install/share/gdown/catkin_pip_env/lib/python2.7/dist-packages/gdown/__init__.pyc'>
 

To make deb file, you have to force install catkin_pip cmake files to /opt/ros/kinetic

sudo cp devel/share/catkin_pip/cmake/*.cmake /opt/ros/kinetic/share/catkin_pip/cmake/
cd src/gdown
rm -fr debian/ obj-x86_64-linux-gnu/ ../../install ../../build/ ../../devel/; catkin_make -C ../../ --make-args debbuild_gdown

Please try with your python package @yuyu2172

My concern is that we have to run pip install during dpkg -i, to create runtme library based on your CUDA environment, and that is not supported by this approach nor dh-virtualenv, fpm...

c.f. #109