(CFACT-63) Add structured processors fact

This commit adds a new 'processors' structured fact, which returns a map
including keys for processor count, physical processor count, and
processor models.

Also, the existing processor facts were updated to take their values from
this new structured fact, rather than resolving them individually.
Ah, that's right. What we did in Ruby facter for this was have them as integers in the new structured fact, but keep them as strings for the flat facts. Should we keep rolling with strings in the structured fact here?