Implemented conditional validators (see #2406)
Fixed getting the count for queries with the union
Fixes #2851.
Merge pull request #2850 from Koudy/db-query-queryScalar

Fixed getting the count for queries with the union
Fixes #2848: Individual queries should be enclosed within parenthesis in a UNION query
Fixes #2825: `Request::getBodyParams()` should correctly parse CONTENT TYPE.
Fixes #2724: consistent use of absolute and relative routes.
Fixes #2823.
fixed test break.
Merge pull request #2808 from drenty/conditional-validator

Implemented conditional validators (see #2406)
separate id and name of attribute for client side validation
Added Validator::whenClient.
reverted breaking PHPdoc codestyle changes

issue #2852
fixed typo
fixed url helper to not prepend to relative URLs
reverted incorrect renaming.
reverted back change to parsing body params.
guide about conditional validator
replaced tabs with spaces in docs.
removed srand()