'Title' column heading misaligned in explorer for users without 'publish' permission

[gasman]

For users without publish permission, the 'order' column of the explorer is omitted. This results in the 'title' column heading being pushed too far to the left:

Rather than adding a special case in the CSS to give it an extra margin, I think it would be cleaner to consistently include the 'order' column all the time (and leave it blank for users without the relevant permission) - that way we avoid additional special-casing further down the line (e.g. #1583 (comment) - adding a row to contain a help message will require <td colspan="5"> or <td colspan="6">). This involves some rewiring of the table logic, though.

[kaedroho]

PR: #1611

You should put the "fixes #1608" bit in the PR body text rather than the title so Github mentions it here.