SW-609: Change all cmake python2 dependecies to python3

CMakeLists.txt

 # $Id: CMakeLists.txt 32985 2015-11-26 11:10:57Z schaap $
 
-lofar_find_package(Python 2.7 REQUIRED)
+lofar_find_package(Python 3.4 REQUIRED)
 lofar_package(sip 0.1 DEPENDS PyCommon LTACommon)
 
 include(PythonInstall)

lib/CMakeLists.txt

 # $Id$
 
-lofar_find_package(Python 2.7 REQUIRED)
+lofar_find_package(Python 3.4 REQUIRED)
 include(PythonInstall)
 
 set(_py_files