Update DropZone and DropZoneItem

[wojtek-krysiak]

Describe the problem feature solves

Right now drop zone is rather raw than final production component. It has to be prettyfied:

Improve mime type Validation

Right now user can give both max size and array of allowed mime types to the component. We have to change that he can also add a group of mime types. Grouls are: audio, image, video, compressed, document, text, PDF, font.

When user gives group there should be a info that user can upload let say image + image icon.

BUT:

• There could be multiple groups
• user could still be able to add mime-types manually
• user can add mimetypes + group so let say group "PDF" + mime type: 'application/vnd.ms-powerpoint' This is not likely but we will have to handle this case

Single/Multi upload

In general: there are 2 modes for this component: single upload and multi upload, and they look the same right now.

The files goes always below the upload box which even takes place when user can upload only one file. We have to change that when upload is single it should go "inside" the upload box.

BUT: user still should see validation information, option to remove the file and upload another one.

For multi upload - it should be similar as now.

Progress bar
I would like to improve upload feature that it upoads to temporary place just after the "drop" so it is instant. In such case user should see a progress bar of uploaded file.