Fix zone named.conf man page documentation
Commit 4ca74eee update the zone grammar such that the zone statement is printed with the valid options per zone type.
This commit is a follow-up, putting back the ZONE heading and adding a note that these zone statements may also be put inside the view statement.
It is tricky to actually print the zone statements inside the view statement, and so we decided that we would add a note to say that this is possible.
Closes #3185 (closed)