[IMP] website snippet new option, gallery

website.snippet: The methods described in javascript will be called automatically from the data-method_name = value on li snippets options. The methods are called in the order relative to children of xml (eg: <li data-method1=value1> ... <li data-method2=value2> ... </ li>, the method1 is then called method2). Methods receive two arguments: type (over, click, reset) and value. data-snippet-id-option becomes data-snippet-id. Several xml options can use the same data-snippet-id.

add a new gallery snippet

convert website_sale to the new option system
[IMP] Use radio widget in various views

+ some UI messages improvements

(Closes #1913)
[IMP] website.theme: add button in customize theme modal to show all theme modules
[IMP] Replace gantt chart lib with dhtmlxgantt 2.1