add YUM proxy repository support

As a systems developer, so that I can minimize downtime, I want to be able to access remote yum packages if the remote yum repository goes down

Acceptance Criteria:

• Access to metadata in SQLLite database format should be blocked
• If proxied metadata is changed, the metadata in the proxy repository will be updated when a package is requested
• Proxy repository must function if the remote repository goes down
  • The proxy will serve what cached components are currently available
• A user with sufficient privilege will be able to run the following commands:
  • yum install <package name/s>
  • yum update <package name/s>
  • yum check-update
  • yum remove <package name/s>
  • yum search <keyword>
  • yum list
• Deleting a yum component should function the same as yum remove, removing the dependencies as well