Update palletjack2pxelinux for PalletJack::Tool
Update palletjack2pxelinux for PalletJack::Tool

Updated palletjack2pxelinux to use the new Tool API. Also updated to
use enumeration via Pallet#children to find `netinstall` objects for
an `os` object in `pxemenu_for_operating_system` instead of searching
the whole warehouse for links.

creideiki/palletjack,creideiki/palletjack,saab-simc-admin/palletjack,notCalle/palletjack,saab-simc-admin/palletjack,notCalle/palletjack