mds: allow to disable [mds] section in ceph.conf if not needed

Added new parameter to ceph::conf (mds_activate) to disable
the [mds] section of ceph.conf if not needed.

Added test for 'default param+mds_activate=false' to ceph.conf.erb.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
manifests/conf.pp: add support for 'mon osd (near)full ratio'

Added new optional parameter to ceph::conf:
- mon_osd_full_ratio
- mon_osd_nearfull_ratio

Added parameter documentation to the manifest.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
pool.pp: add new define ceph::pool

Added new ceph::pool to manage pools. Currently these actions are supported:
- create a new pool (via $create_pool, defaults to false)
- delete an existing pool from the cluster (via $delete_pool, defaults to
  false) -> BE VERY CAREFULLY WITH THIS PARAMETER!
- increase pg_num of a pool (via $increase_pg_num, defaults to false)
- increase pgp_num of a pool (via $increase_pgp_num, defaults to false)

fixed typo in 'describe' of ceph_key_spec.rb (s/wen/when/).

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
README.rst: add hint on how to run the rspec tests

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>