06-AddingCartridges: Delete reference to bundle

Delete "bundle" from the list of tools used because we do not use Bundler
in this lab.
Switch from RHN to RHSM

Chapters/02-SubscriptionManagement.md, Chapters/03-Installation.md: Switch
from using rhn-channel (RHN) to using subscription-manager (RHSM).
06-AddingCartridges: oo-admin-yum-validator

Chapters/06-AddingCartridges.md:
* Describe oo-admin-yum-validator and instruct the student to use this
  command to enable the JBoss channels before trying to install the JBoss
  cartridges.

* Describe the oo-admin-cartridge command and instruct the student to use
  this command to list the available cartridges after installing new
  cartridges.

* Mention the MCollective agent and instruct the student to restart
  MCollective after installing new cartridges.
03-Installation: Recommend GNU Screen

Recommend that the user start a GNU Screen session with logging enabled
before running openshift.sh.
04-VerifyInstall: Delete ActiveMQ (Jetty) console

Chapters/04-VerifyInstall.md:
* Delete mention of the ActiveMQ (Jetty) console, which is no longer
  configured or enabled by the installation script.
* Fix a typo: "very" should be "verify."
06-AddingCartridges: Delete mention of Jenkins

Chapters/06-AddingCartridges.md: Don't mention the Jenkins cartridges in
this lab; they are installed only later, in Chapters/19-Jenkins.md.
06-AddingCartridges: Augment diagnostics

Chapters/06-AddingCartridges.md: Because we mention
/usr/libexec/openshift/cartridges, also mention the location of the
cartridge repository and other information about installed cartridges.
Merge pull request #2 from Miciah/master

Various installation fixes