[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
typo

s/nonexiting/non-existing
Merge pull request #1945 from MadeleineHero/master

[FIX] typo
[ADD] website slides module
[FIX] broken view xml
[REF]: refactor clides to adapt channel concept
[IMP]: implement like button
[IMP]: add like button on slide detail view
[IMP]: different aspect ratio for slide and video
[IMP]: improve channel landine page
[IMP] imporve like/dislike feature on slideview
[IMP]: implement channel gridview
[IMP] small layout improvement
[IMP]: improve subscrive view on channel page
[IMP]: small improvement, added back button beside titles
[IMP]: small improvements
[FIX]: small fix for creating slide
[FIX]: small improvements