There have been some z-indexes that were removed and then reintroduced
through strange merges. This is an attempt to remove all z-indexes that
are unnecessary and to clearly state the purpose of the remaining
z-indexes in a comment to each index.
SPR-981
The `margin-top: 0` overwrites DokuWiki's default `margin-top: -1.4em`
and causes the edit button to be far below the section it is supposed to
edit. This causes a visual disconnect between button and section,
especially for small or empty sections. This is even more
apparent when contrasted with the button-placement for tables etc.
