emg: Added emg sensor C source

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

    * Renamed all files with groveemg to emg
    * Replaced all instances of groveemg with emg
    * Added C source for emg sensor
    * Updated all cmake files
    * Added C example for emg sensor

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

src/groveemg/pyupm_groveemg.i

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