changelog: Added entries for recent python modules changes
changelog: Added entries for recent python modules changes

Updated the changelog.md to reflect the recent python modules changes.
Added a vnext which can be replaced with the next UPM release version
number.

Signed-off-by: Noel Eck <1e36ab6ededef40f3f16bdbc1b09eee72c5d08cf@intel.com>

spitfire88/upm,jontrulson/upm,g-vidal/upm,intel-iot-devkit/upm,pylbert/upm,skiselev/upm,malikabhi05/upm,nitirohilla/upm,jontrulson/upm,Propanu/upm,g-vidal/upm,Jon-ICS/upm,nitirohilla/upm,intel-iot-devkit/upm,Propanu/upm,Propanu/upm,whbruce/upm,pylbert/upm,nitirohilla/upm,sasmita/upm,Jon-ICS/upm,whbruce/upm,sasmita/upm,intel-iot-devkit/upm,stefan-andritoiu/upm,stefan-andritoiu/upm,malikabhi05/upm,stefan-andritoiu/upm,spitfire88/upm,Jon-ICS/upm,spitfire88/upm,Propanu/upm,nitirohilla/upm,malikabhi05/upm,sasmita/upm,nitirohilla/upm,Jon-ICS/upm,Propanu/upm,jontrulson/upm,g-vidal/upm,spitfire88/upm,malikabhi05/upm,g-vidal/upm,stefan-andritoiu/upm,malikabhi05/upm,whbruce/upm,pylbert/upm,spitfire88/upm,Propanu/upm,skiselev/upm,jontrulson/upm,whbruce/upm,sasmita/upm,malikabhi05/upm,skiselev/upm,intel-iot-devkit/upm,whbruce/upm,stefan-andritoiu/upm,pylbert/upm,g-vidal/upm,g-vidal/upm,pylbert/upm,sasmita/upm,intel-iot-devkit/upm,Jon-ICS/upm,skiselev/upm,pylbert/upm,skiselev/upm,jontrulson/upm,stefan-andritoiu/upm,skiselev/upm,intel-iot-devkit/upm