netteForms.js: declared variable `values`
Http\Response: enabled custom status codes
netteForms.js: getAttribute() returns empty string in old browser when the attribute does not exist [Closes #1193]
Environment: DI container class is named EnvironmentContainer instead of SystemContainer

It prevents "Compile Error: Cannot redeclare class SystemContainer" when another container is later created by Configurator, and shows correct error "SystemContainer has already been created automatically by Nette\Environment"
Nette\Framework: added constant VERSION_ID