light: Added light sensor C source

Added the C source for the light sensor with necessary changes to cmake,
examples, docs.

    * Renamed all files with grovelight to light
    * Replaced all instances of grovelight with light
    * Added C source for light sensor
    * Updated all cmake files
    * Added C example for light sensor
    * Split out light sensor from grove library

Signed-off-by: Noel Eck <noel.eck@intel.com>

src/light/pyupm_light.i

@@ -0,0 +1,11 @@
+// Include doxygen-generated documentation
+%include "pyupm_doxy2swig.i"
+%module pyupm_light
+%include "../upm.i"
+
+%feature("autodoc", "3");
+
+%include "light.hpp"
+%{
+    #include "light.hpp"
+%}