Add errata field to package

If the errata field is specified for a package, this will be sent to the mead
scheduler when adding to errata or when scheduling a build; it will override the
current settings we have for errata.
Fix version check in ETT

Since the mead field is being deprecated, call the correct method to get the
mead nvr instead.
Merge pull request #145 from thescouser89/cronjob_modes

Cronjob modes