996198 - CDS sync should not attempt to sync older packages which have been removed from RHUA by way of 'num_old_packages_keep'

Added part of the functionality for the cdsplugin to parse 'sync_data' and pull out options to limit syncing older packages.
Two ways exist to limit syncing older packages on a CDS
1) RHUA sends options through sync_data
2) CDS config file is able to override any settings from RHUA