Update formatting in compliance with pep8 with the following exceptions:
* truncate to 120 characters in line
* prefer double quotes `"` to single quotes `'` in strings
Switch addon lookup mechanism from parsing html page to extracting info
from .gitmodules file.
This simplifies logic and allows using non-Github repos.
Readme for Github repos are extracted from HTML pages using regex.
Gitlab pages are converted to HTML using Python Markdown lib if present,
falling back to displaying raw markdown.
In this case image links are converted from relative to absolute paths.
Correct crash when Macro description is not reachable
Python crashed when under proxy - Macro list is charged - Proxy is undone ( internet connection lost) - Try to load macro description (u=None)
Add Proxy setting in Addon Manager Option UI
Correction of SSL context
Replace ssl.Purpose.CLIENT_AUTH by ssl.Purpose.SERVER_AUTH as context for a client
Add configuration of proxy setting UI
Add proxy management by urllib
Separate the Macro class of the AddonManager into addonmanager_macro.py
to prepare for future support for dependent files for macros from the
git repository.