CONTENTBOX-219: Pretty significant revamp of widget views to consolidate...

.... Also refactored code to separate widget list vs widget preview modes; now the preview/test mode can be used really easily when not inserting/editing a widget

CONTENTBOX-364: Consolidated widget views a bunch. Also trimmed down CSS for widgets enough to be able to remove the custom CSS that was used before. Also updated the width of widget viewlets to expand by percentage to fill up the content area a bit better.