- Data is now stored in three separate files for items, assignments and rules. File format is simpler.
- Removed `authFile`. Added `itemsFile`, `assignmentsFile` and `rulesFile`.
- `createdAt` and `updatedAt` are now properly filled with corresponding file modification time.
- `save()` and `load()` are now protected instead of public.
- Added unit test for saving and loading data.

works on windows out of the box now.
fixes #3989

fixes issue #3989

[ci skip]

1. Added proper handling and support of the symlinked directories.
2. Added $options parameter.

Fixes #1452: Added `Module::getInstance()` to allow accessing the module instance from anywhere within the module

Fixes #4071: `mail` component renamed to `mailer`, `yii\log\EmailTarget::$mail` renamed to `yii\log\EmailTarget::$mailer`