massive refactoring to switch from camelCase to snake_case:

historically, Libervia (SàT before) was using camelCase as allowed by PEP8 when using a
pre-PEP8 code, to use the same coding style as in Twisted.

However, snake_case is more readable and it's better to follow PEP8 best practices, so it
has been decided to move on full snake_case. Because Libervia has a huge codebase, this
ended with a ugly mix of camelCase and snake_case.

To fix that, this patch does a big refactoring by renaming every function and method
(including bridge) that are not coming from Twisted or Wokkel, to use fully snake_case.

This is a massive change, and may result in some bugs.

sat/plugins/plugin_xep_0203.py

@@ -51,7 +51,7 @@ class XEP_0203(object):
         log.info(_("Delayed Delivery plugin initialization"))
         self.host = host
 
-    def getHandler(self, client):
+    def get_handler(self, client):
         return XEP_0203_handler(self, client.profile)
 
     def delay(self, stamp, sender=None, desc="", parent=None):