Improvements in the upload of files

Show progress bars and improve the upload of files, logos and avatars in general.
Now there's a `@bind` and a `@bindCrop` in this class.
`@bind` is automatically called from `mconf.Resources`, which makes it more automatic. But apparently it's not being used any more (there are no elements using the class `.form-for-crop`).

My suggestion would be:
* Remove `@bind`
* Rename `@bindCrop` to `@bind`
* Remove old calls made to `@bindCrop` (I found 2, in spaces/edit and profiles/edit) and add a single one in `mconf.Resources`. This would make it bind automatically so it doesn't need to be called in every js that needs it.
* `@bind` ideally should expect elements of a class to bind the crop into, not an ID, as in `cropModal = $("#crop-modal")`.