Previously, when reading old configurations, confTool would merge
together the two dictionaries that were written.  This is needed
for proper handling of JobOptionsSvc; the properties we want to compare
are those from the second dictionary.  (The first dictionary
contains properties such as the search path which we want to ignore.)
This was changed when confTool was unified for the old and new
configurations.  Tweak it to get back to the previous behavior.

- Now the diff option does not treat as different 'True' vs True.
- In case of different order in lists that fact is printed instead of printing diff of each of its elements

Now using this option, when component exists in only one configuration, nothing is printed.

 - Merged with https://gitlab.cern.ch/emoyse/Scripts/blob/master/comparePickledConfig.py by Edward Moyse
 - python 2 and 3 compatible
 - Functionality:
  - diff of a .pkl and .json files (can diff any combination)
  - converting .pkl file to .json and .json to .pkl
  - parsing only specified components (if wanted))
  - printing whole configuration as well as conponents included

Initial python3 port.  Not intended to be complete yet; only that required
for basic athena/configuration jobs.

Former-commit-id: d3f7be6c

Former-commit-id: 85fe7791