Fixes for the ceilometer installation on RHEL

- install and start the alarming services
- configure the mongo listen interface
- add missing dependencies for the compute agent (workaround for a
  packaging bug)

Closes-Bug: #1308638
Change-Id: Ib739c50e26cf1ccc16f87b45695388ba358e0df3
Updated Weighting section

Put in tables of relevant weighting options for both hosts
and cells. Updated intro. Added graphic from training
guides (moved into common and relinked in training guide).

Closes-bug: #1261521

Change-Id: Ic9fd323e31016040dbbf18be4969ff829d4edf1e
Merge "Updated Weighting section"
Merge "Fixes for the ceilometer installation on RHEL"