Forms, group labels

* Form renderer now respects group labels and names
Forms, group class

* Form renderer respects container class
Forms, containers

* Added outer_class attr to form container
* Inner class respects container type
Forms, rendering containers

* Form renderer doesn't draw empty containers
Forms, tabs returns

* Form method tab() returns container instance instead of form instance
Forms, tabs, rendering

* Form renderer respects tab classes
Forms, renderer, multicheckbox

* Multi input inputs are rendered with input container
Forms, renderer, multicheckbox

* Multi inputs carry usable css classes
Attr, Database models to_html

* Added method to_html to attr and database model
Global to_html compatibility

* Merged compatibility of to_html methods
[fix] Attr, Database models,  to_html

* Fixed to_html translations of attr and database models
Locales, common attrs

* Added getting common attribute translations
Tags: to_html

* Don't convert objects in html attribute values to html