New forms proposal

Phase 1: Implementation
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Overview
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As the need for creating forms that can be rendered (in view) and validated (in controller) we decided to introduce new to create of forms. 

Firstly we tried to do it as a service but it wasn't best way. After consultations with TechLeads we designed and developed other approach that can be seen here. Main point of this solution is fact that every form should be an object and Form objects should be able to render themselves (whole form or by parts).

Goals
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Create an easy way to create form in Wikia code base that can be easily:
* rendered
* validated (using existing WikiaValidators)
* reused

Examples
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Some code examples can be found in includes/wikia/forms/examples

Next steps
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* _Phase II_: Collect feedback from devs and add improvements
* _Phase III_: Cover code with unit tests
* _Phase IV_: Rewrite some of existing forms into new Form builder

@All-devs: Feel free to add your feedback in comments, so we can make it more usable for everyone.
@owend @federico-lox Can you guys see if everything is ok?