Added System Facts generator method.

When creating a new system via the API, one can also specify system
`facts` so that information about the underlying operating system and
hardware can be processed and displayed by the web ui. Furthermore, this
type of information is used internally by `Candlepin` to determine
whether your `Satellite` system has enough (and the right type of)
subscriptions to make your system fully compliant.
Merge pull request #1257 from omaciel/system-facts

Added System Facts generator method.