Yaml configurable forms

[calina-c]

Hello and, first of all, thank you for the wonderful library @kristijanhusak. I have been using it for my Laravel project and I enjoy it a lot.

That being said, I have a suggestion on how to improve the form builder by adding YAML support. I have written a YamlConfigForm class in my project, which takes a .yml file as a parameter and builds the form according to the file contents. I have also added support for callbacks. I will attach some examples below.

I believe integrating this feature will help with:

• removing code duplication arising in similar forms
• improving clarity of reading form configurations

I will be happy to fork the repository myself and add this functionality, if it is something you would welcome.

Example gists (of course these are adapted to my needs, but they can be generalised as necessary):

• YamlConfigForm: https://gist.github.com/calina-c/926a0281724e95fea9df5c9f7d8d9756
• Yml file example (ALL_CAPS are custom callbacks and methods): https://gist.github.com/calina-c/647c02a9e46f08347adf95973de4b440
• Example showing that the form is still extensible for less generic modifications: https://gist.github.com/calina-c/1d0bdfb063999237072f617310e27f02

Thank you again for the wonderful library and let me know if I can help! :)