…screen, database) out of the logger and into the LoggerFactory

…clarity

…sor" objects (to prepare the transition to Monolog)

…matters instead of events

…ease future transition

…olog naming

… StreamHandler

…ment

…tainerFactory

This class can be used in tests to create a specific environment (e.g. the prod environment, CLI environment, etc...)

…Handler

This is so the FileHandler can be replaced by Monolog's StreamHandler

…eamHandler

We can't remove FileHandler completely because it generates a custom exception message in case of error.

…s disabled in tests

…ables now that we have a container

…a processor + added tests

Monolog handlers support 1 formatter. Using processors instead of nested formatters leads to much simpler code.

In the tests, logging is disabled. But not when testing the logger itself…

… logging

- the error handler logs warnings and notices, and turns errors into exceptions (`ErrorException`)
- the exception handler catches all uncatched exceptions and display them to the user (HTML or CLI)
- the "screen" logging backend has been removed
- I've normalized exceptions/errors shown to the user in HTML (wether they are catched by the FrontController or not)

…L notifications

The "screen" backend (WebNotificationHandler) now logs to HTML notification boxes using the `Notification` api.
I've re-set the default log level to WARN, and logged PHP notices/warnings to "warning" so that on a default install they are shown in the page in a yellow/warning notification box.

For the record, the default log level had previously been changed from WARN to ERROR because screen logging was previously messing the HTML/JSON output (which was breaking archiving). With the logger refactoring this is no longer a problem.

Cannot add tests for the screen backend because I would need to mock the session, which is not possible right now because it's all static stuff.

…ggerInterface

- log_only_when_cli
- log_only_when_debug_parameter

Refactored the logger to use PSR-3 and Monolog (#6622)