Add basic Findscript for DepthSense SDK

As per subject.

The find script is essentially a modified copy of `FindTinyXml.cmake` from `cmake_modules`. I could've used a random one found on the web, but this one seems to follow 'ROS cmake practices'.

`catkin_lint` outputs a warning about modifying `CMAKE_MODULE_PATH`, but I could not find any better (more catkin-y) way of getting CMake to find a local find script (afaik the script is not needed by dependent pkgs, so `CFG_EXTRAS` doesn't seem right).

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I've left the `include_directories(..)` statement referencing `suitesparse` in, but commented it. Does not seem to be needed on my machine. I think it can be removed.