Explicit CM component install and repo management

[ggear]

Address the following:

• Explicit CM repo installation, shared between roles
• Define CM Server version to be installed
• Define CM Agent role and installer (cmagent)
• Ensure CDH Client is in sync with whirr-core
• Automate CM configuration

[ggear]

I intend to work on this here:

https://github.com/ggear/whirr-cm/tree/graham-patch-ISSUE-12

[ggear]

Note that the branch backed by this pull request (https://github.com/ggear/whirr-cm/tree/graham-patch-ISSUE-10+12) includes fixes to #10 and #12, which would conflict otherwise