E2iPlayer: porting py2 code to py3 as of 09/05/2021

The target is to create py3 compatibility layer which will allow to auto convert py2 code to py3 without need of manual intervention.
Next step will be adopt/compile C python 3 modules like pycurl (already done for i686), subparser, e2ivalidator for all supported platforms.
e2icjson module used in py2 will be replaced with ujson.

The main repo will be still py2, code from py2 repo will be auto synchronized with py3 branch.