U4-7182 - Replace the media image grid with flexbox

Issue is part of PR: https://github.com/umbraco/Umbraco-CMS/pull/831

Code seems good from glancing over it, will start testing now.

The only TODO so far is to remove the old code files that was creating the image grid. This is a 'breaking' change but that should not have been used though we can list it as a break in the tracker.

Bug #1

When navigating to the thumbnail list and then back to the list view I get multiple JS errors:

TypeError: (t || "").match is not a function
    at Object.x.event.remove (jquery.min.js?cdv=1102612678:5)
    at HTMLDivElement.<anonymous> (jquery.min.js?cdv=1102612678:5)
    at Function.x.extend.each (jquery.min.js?cdv=1102612678:4)
    at x.fn.x.each (jquery.min.js?cdv=1102612678:4)
    at x.fn.extend.off (jquery.min.js?cdv=1102612678:5)
    at umbraco.directives.js?cdv=1102612678:4130
    at Object.e.$broadcast (angular.min.js?cdv=1102612678:94)
    at Object.e.$destroy (angular.min.js?cdv=1102612678:91)
    at angular.min.js?cdv=1102612678:157
    at angular.min.js?cdv=1102612678:100

The JS in the umbraco.directives.js that seems to be the issue is:

scope.$on("$destroy", function(){ elm.off(f);} );

All looks good apart from the js bug mentioned

I've also pushed some updates

js error bug #1 fixed: https://github.com/umbraco/Umbraco-CMS/commit/8d81d9922cb685cc21a122d50ee7ee0f7821cb10