remove empty message arrays

Added support of deferred validation.

Added support of deferred to ```ActiveForm``` validation.

fixes #4482

fixes #4480

Mistype

fixes #4470

Remove nonsense branch logic

4469 compare string without shortcut

translations for this week

[wait for proofreading]roughly translate tutorial-core-validators

missing word. [skip ci]

typo fix

Typo in docs

not sure about L421

fix the link

Fixes #4131: Security adjustments

Security component adjustments: fixed comment style, hkdf() and pbkdf2() are now protected, compareString() is now public

Fixes #4453: `yii message/extract` wasn't properly writing to po files in case of multiple categories

Corrected table name

Update schema-mssql.sql