Java Edition 1.13-pre3

1.13-pre3 is the third pre-release for 1.13.

Changes

 * Major memory usage optimizations
 * The resource pack folder  got renamed to.
 * The resource pack folder  got renamed to.
 * Blockstate files
 * for blocks without block states changed to an empty string.
 * Item Frames now have  instead of   and   instead of.
 * Model references no longer start at the  folder, but instead at.