First attempt at linking system ROS on armv7l

First attempt at linking system ROS on armv7l.
Point Robustus-installed ROS overlays at system ROS

Point Robustus-installed ROS overlays at system ROS.  First attempt.  Untested.
Added missing "import platform" statement

Added missing "import platform" statement.
Further refinements for ROS overlay with system ROS

Further refinements for ROS overlay with system ROS.
Refinements of ROS overlay pointing to system ROS

Refinements of ROS overlay pointing to system ROS.
Additional non-ROS ROS Python dependencies for project venv

Additional non-ROS ROS [sic] Python dependencies for project virtual environment.
Added ROS ROS [sic] dependencies for installation in venv

Added ROS ROS [sic] dependencies for installation in Python virtual environment.
I feel this should not be necessary.
Merge branch 'master' of github.com:braincorp/robustus into kulungowski_robustus
Retrieve compiled ROS overlays from remote Robustus wheelhouse

Retrieve compiled ROS overlays from remote Robustus wheelhouse.
Added imports

Added imports.
Build "venv" ROS if no system ROS, delete ROS "src"

Build Python virtual environment ROS if no system ROS and delete ROS source/build
directory.
If no system ROS, attempt to download/install compiled ROS

If no system ROS, attempt to download/install compiled ROS from remote Robustus
archive.
Added imports

Added imports.
Added more "import"s

Added more "import"s.
Added further imports, clarified output message in "install_sip.py"

Added further imports, clarified output message in "install_sip.py".
Enable both system and non-system ROS installs

Enable both system and non-system ROS installs.  This requires an additional value
to be used for hashing ROS overlays: the directory of the ROS install.
Fully undid only partially undone change

Fully undid only partially undone change.
Restoring original version of "catkin_pkg"

"catkin_pkg==0.2.2" (on "master") -> "catkin_pkg==0.1.24"
Restoring new version of "catkin_pkg"

"catkin_pkg==0.1.24" -> "catkin_pkg==0.2.2" (on "master")
New version of "catkin_pkg" for ROS overlays

"catkin_pkg==0.1.24" (on "master") -> "catkin_pkg==0.2.2"