Add Proxy to Addon Manager with UI

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

src/Mod/AddonManager/addonmanager_macro.py

@@ -103,6 +103,9 @@ class Macro(object):
         except:
             print("AddonManager: Debug: unable to open URL",url)
             return
+        if u is None :
+            print("AddonManager: Debug: connection is lost (proxy setting changed?)",url)
+            return
         p = u.read()
         if sys.version_info.major >= 3 and isinstance(p, bytes):
             p = p.decode('utf-8')