Support full file issues reported at line 0

[La0]

With this code, the licence checks are now reported: Example on phab-dev

The coverage issue are now also considered full file issues (which makes sense too)

Fixes #230

[marco-c]

We could instead make the license analyzer follow our JSON standard and make it return None instead of 0 as the line

[marco-c]

We could instead make the license analyzer follow our JSON standard and make it return None instead of 0 as the line

As discussed on IRC, let's support 0 as None, but let's log an error on Sentry so we can fix analyzers that use 0 to mean full file to use None instead, and analyzers who use 0 as first line to add +1 to their lines.

[La0]

@marco-c I updated the bot's code to send a warning on line 0, and falling back to full file mode