as "type primary" is preferred over "type master" now, it makes
sense to make "primaries" available as a synonym too.
added a correctness check to ensure "primaries" and "masters"
cannot both be used in the same zone.
(cherry picked from commit 16e14353b1)
The ARM and the manpages have been converted into Sphinx documentation
format.
Sphinx uses reStructuredText as its markup language, and many of its
strengths come from the power and straightforwardness of
reStructuredText and its parsing and translating suite, the Docutils.
(cherry picked from commit 9fb6d11abb)
