During development we still want to use a cache to cache items that are requested multiple times during one request. For example Marketplace API calls. The marketplace page in dev mode does now load in about 4 seconds instead of 30 seconds. Also plugin components etc. will now longer loaded multiple times.

Translations are now lazily loaded instead of being explicitely loaded by other components (e.g. the front controller, the plugin manager, etc...). Now other parties only configure "directories" where the translator can find translations. That makes the translator decoupled from the rest of Piwik.

fixes #6895 - add a config option that causes the image graphs to show the evolution within the selected period instead of the evolution across the last n periods

Initially we considered dropping the `ini` config, but the current stance is we keep `config.ini.php` because it's a user friendly config.

- log_only_when_cli
- log_only_when_debug_parameter

Fixes #6529 before loading plugins in memory, order the list the same as it is in global.ini.php  - then load remaining plugins in alphabetical order

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.

Applying review changes: remove tracker_ prefix from config names, move shouldForceNewVisit to VisitDimension and simplify triggerPredicateHookOnDimensions.

- 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)

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

Refs #2624, add INI config options that will force a new visit if campaign/website referrer information changes between actions. Includes new tracker hook shouldForceNewVisit that dimensions can use to force a new visit during tracking. Also includes light refactoring to referrer dimensions. Testless.

fixes #6824 Hash the fingerprint with the website ID to make it different on each website for a given user + tests

#6622 Logger refactoring: simplified the formatters by merging ExceptionHtmlFormatter and ErrorHtmlFormatter

`Piwik\Log` is now a wrapper on top of Monolog. The real logger can now be injected using `Psr\Log\LoggerInterface`.

- follows the verbosity level
- formatted with colors

#6622 Logger refactoring: moved "log message processing" into "Processor" objects (to prepare the transition to Monolog)