doc: create an index/toctree only for man pages

Signed-off-by: Alfredo Deza <adeza@redhat.com>

doc/man_index.rst

@@ -0,0 +1,43 @@
+.. this is the man index/toctree reference. It is separate from the "regular"
+.. index so that it doesn't include things that are not tagged for man pages
+
+.. toctree::
+   :maxdepth: 3
+   :hidden:
+
+   man/8/ceph-authtool
+   man/8/ceph-clsinfo
+   man/8/ceph-conf
+   man/8/ceph-create-keys
+   man/8/ceph-debugpack
+   man/8/ceph-dencoder
+   man/8/ceph-deploy
+   man/8/ceph-detect-init
+   man/8/ceph-disk
+   man/8/ceph-fuse
+   man/8/ceph-mds
+   man/8/ceph-mon
+   man/8/ceph-osd
+   man/8/ceph-post-file
+   man/8/ceph-rbdnamer
+   man/8/ceph-rest-api
+   man/8/ceph-run
+   man/8/ceph-syn
+   man/8/ceph
+   man/8/crushtool
+   man/8/librados-config
+   man/8/monmaptool
+   man/8/mount.ceph
+   man/8/osdmaptool
+   man/8/rados
+   man/8/radosgw-admin
+   man/8/radosgw
+   man/8/rbd-fuse
+   man/8/rbd-ggate
+   man/8/rbd-mirror
+   man/8/rbd-nbd
+   man/8/rbd-replay-many
+   man/8/rbd-replay-prep
+   man/8/rbd-replay
+   man/8/rbd
+   man/8/rbdmap