Add an easier way (template tag?) to retrieve the template used for the current page

[mleroi]

Right now we retrieve this info in screen:show via current_view.template_name :
App.on( 'screen:showed', function( current_screen, current_view ) {
console.log(current_view.template_name);
} );

And, before all, I should write the doc about this screen:show event !

[mleroi]

TemplateTags.getCurrentTemplate() added and doc made for screen:showed event :)
http://uncategorized-creations.com/wp-appkit/doc/#183-screenshowed