No column heading for checkbox column decreases accessibility

[littlesvensson]

Bug description
The heading elements of the columns with checkboxes do not have a textual heading. Therefore, the screen reader takes the label of the included checkbox, which leads to confusing outputs when navigating through the records of the table.

Steps to reproduce
Steps to reproduce the behavior:

1. Go to for example All findings view.
2. Navigate to the first column (where only checkbox it) with a screenreader and let it "read" what the column is about.

Expected behavior
A meaningful heading should be available for the mentioned columns.