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/tools/web.py

@@ -74,7 +74,7 @@ class NoCheckContextFactory:
 treq_client_no_ssl = HTTPClient(http_client.Agent(reactor, NoCheckContextFactory()))
 
 
-async def downloadFile(
+async def download_file(
     url: str,
     dest: Union[str, Path, BufferedIOBase],
     max_size: Optional[int] = None