Match old alias behavior when migrating.

Previously the alias system would pass all arguments from the alias
to its command(s) implicitly. The new system requires arguments to be
explicitly passed so server owners can have more control over where and
how they are passed. To ensure this isn't a breaking change during the
migration from bukkit.yml to commands.yml we now add the $1- argument
to the alias commands to match the previous behavior.
Readd BlockPlaceEvent for half slab to full block. Fixes BUKKIT-5390