Accessibility Issues in FileList component

[marcus-herrmann]

Steps to reproduce

1. Use Phoenix with assistive technology, such as: Screen Reader

Expected behaviour

The user should know of the existence of every interactive element and their functionsthe contents of every table column by label table headers.

Actual behaviour

Most of the checkboxes are unlabeled, the files or folder controls are semantically the wrong element (covered in #2317), some table headers appear empty:

1. This table header item/column header conains just an unlabel checkbox, therefore no text information that could serve as label
2. This table header item/column header is completely empty
3. This checkbox is not labelled
4. This star image is semantically speaking not a control but a clickable div (covered in ODS PR Refactor and document OcStar(Toggle) owncloud-design-system#525)
5. This File/Folder label is also just a clickable span (covered in Middle click to file/folder open in new tab #2317)

(The rest of the issue template is irrelevant to the kind of this issue)