python: Added upm directory for python modules

* Grouped UPM python modules into upm directory, for example:
      /usr/local/lib/python2.7/dist-packages/upm
    * Updated UPM example import statements
    * Removed unused RPATH statements from UPM src CMakeLists.txt,
      currently build collateral contains an explicit RPATH which
      is stripped from the install collateral.
    * Converted python examples to work on both python2 AND python3
    * Added ctest for loading examples w/python3
    * Removed returns from swig macros
    * UPM python module use will change...
        Before:
            import pyupm_dfrph
        After:
            from upm import pyupm_dfrph
            or
            import upm.pyupm_dfrph
            etc...
    * This commit fixes #468

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

examples/python/o2.py

@@ -21,8 +21,9 @@
 # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
+from __future__ import print_function
 import time, sys, signal, atexit
-import pyupm_o2 as upmO2
+from upm import pyupm_o2 as upmO2
 
 def main():
     # This was tested with the O2 Oxygen Concentration Sensor Module
@@ -36,7 +37,7 @@ def main():
 
     # This lets you run code on exit, including functions from myO2
     def exitHandler():
-        print "Exiting"
+        print("Exiting")
         sys.exit(0)
 
     # Register exit handlers
@@ -44,8 +45,8 @@ def main():
     signal.signal(signal.SIGINT, SIGINTHandler)
 
     while(1):
-        print "The output voltage is: {0}mV".format(
-        myO2.voltageValue())
+        print("The output voltage is: {0}mV".format(
+        myO2.voltageValue()))
 
         time.sleep(.1)