I'm working on a CMS where administrators can edit the design of the frontend website (think in the kind of stuff you can do in Wix or Weebly). It's a combination of handmade and third-party jquery plugins and plain javascript: colorpickers, fileuploaders, image cropping, div resizers, styled checkboxes, gradient generators, and so on...
This designing interface is (for today standards) a bit clunky and we want to renovate it and, at the same time, replace those third-party components with a more integrated tool.
So, I'm looking for a framework/library with this features: modern look & feel and ui components, appropriate for a design application. I know there is Bootstrap, Semantic, Foundation, but they have only basic widgets like buttons, tabs, menus...
I prefer open source and free like Webix, KendoUI Core, OpenUI5, Qooxdoo and AlloyUI (or any other tool that you know), but I have never worked with them and I would like to get feedback for my specific case.
Example: AlloyUI caught my attention, with good documentation and interesting components (colorpicker, image cropper, sortable layout, resize, drag & drop) but is based on YUI, a now defunct project. Would you recommend it anyway?
I'm open to any suggestion!