Add iconcrack_[id] for PlayEffect

This allows users to use
- playeffect <player.location> iconcrack_268
to display an item break effect for any block or item.
Fix YAML command bug

- yaml write:KeyName id:MyId
currently throws an NPE, so you have to do
- yaml write:KeyName value: id:MyId
to make a blank key. This commit allows the former.

This also fixes a problem with PlayEffect from the previous commit