Add posibility to autoformat HTML source

[zeleznypa]

I'm using CKEditor extra few days and manytimes I need to modify HTML source code.
Currently the CKEditor generate strange code format whitch is uncomfortable to edit.

I found great CKEditor plugin HTML Output Writer which provide posibility of setting indentation and break around tags.

Currently I use this settings

        editor.on('instanceReady', function( ev ){
            var index;
            var indentedTags = ["div","header","nav","ol","p","section","ul"];
            for (index = 0; index < indentedTags.length; ++index) {
                ev.editor.dataProcessor.writer.setRules( indentedTags[index] , {
                    indent: true,
                    breakBeforeOpen: true,
                    breakAfterOpen: true,
                    breakBeforeClose: true,
                    breakAfterClose: true
                });
            }
        });

It could be usefull to have indentedTags as system configuration.