Multiple fix and enhancement

[fabienwnklr]

In first, sorry for this big PR, it's only simple commits but next time I’ll be careful ..

So, i explain all my commits :

• Fix: remove check 'invalid' for open dropdown : this cancel opening dropdown
• Fix: hide clear_button if value empty : Clear button always visible on clear value
• Fix: $.trim and $.isArray fn deprecated : Remove deprecated JQuery method
• Style: empty option look like selectable : revert from Fix: revert wrong commited for testing
• Fix: remove 'singleClose' from 'remove_plugin' assumed now by 'clear_… : remove method 'singleClose' from 'remove_plugin' , cause now assumed by 'clear_button' plugin
• Fix: displaying clear btn if value present : on error with Fix: hide clear_button if value empty
• Fix: remove class active on removing item : Remove active class when item removed cause it retaining active class when reselecting it
• Fix: don't execute remove_button plugin for single select : Otherwise the style apply to single select
• Fix: retrieve data as string : revert from [Fix: retrieve all data attributes with style/class atrributes for opt…](c9ed4e8)
• Feat: add 'isJSON' util function : Implement util function isJSON
• Fix: retrieve all data attributes with style/class atrributes for opt… : as mentioned above, retrieve all data attributes and merge on one object for use it if necessary
• Fix: add style and class attributes to option template : Use class and style attribute for option rendering
• Fix: concatenation classes options : simple fix for classes concatenation
• Test: update test wrong and add test for class/style attributes : I update old test broken with my last modification on options object and add test for using style and class attributes on option