vdiv: Added vdiv C source.

Multiple changes related to building the vdiv c source w/c example.

    * Renamed GroveVdiv to vdiv (all cases) throughout source, examples,
    directory names, and documentation.

    * Added C source.

    * Tested C sensor code on edison

    * Updated CMakeLists.txt for examples-c to build from
    <sensorname>-c.  This was a small change to get c examples to build
    for sensors in which the C++ does NOT wrap the C.

    * Added C example for vdiv.

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

src/grovevdiv/CMakeLists.txt

@@ -1,5 +0,0 @@
-set (libname "grovevdiv")
-set (libdescription "upm grove voltage divider module")
-set (module_src ${libname}.cxx)
-set (module_hpp ${libname}.hpp)
-upm_module_init()