o2: Added O2 sensor C source

Added the C source for the O2 sensor with necessary changes to cmake,
examples, docs.

    * Renamed all files with groveo2 to o2
    * Replaced all instances of groveo2 with o2
    * Added C source for o2 sensor
    * Updated all cmake files
    * Added C example for o2 sensor

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

examples/java/CMakeLists.txt

@@ -44,7 +44,7 @@ add_example(GroveMDSample grovemd)
 add_example(GroveMoistureSample grovemoisture)
 add_example(GroveMQ3 gas)
 add_example(GroveMQ9 gas)
-add_example(GroveO2Example groveo2)
+add_example(O2Example o2)
 add_example(GroveQTouch at42qt1070)
 add_example(GroveRelaySample grove)
 add_example(GroveRotarySample grove)

examples/java/O2Example.java

@@ -22,15 +22,15 @@
  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
-import upm_groveo2.GroveO2;
+import upm_o2.O2;
 
-public class GroveO2Example {
+public class O2Example {
 
 	public static void main(String[] args) {
 		// TODO Auto-generated method stub
 		//! [Interesting]
 		// Initializing the Grove O2 sensor on the A) analog pin
-		GroveO2 o2 = new GroveO2(0);
+		O2 o2 = new O2(0);
 
 		while(true){
 			System.out.println("The output voltage is: "+o2.voltageValue());