Fix #1276

Signed-off-by: Ross Allan <rallanpcl@gmail.com>
Merge pull request #1277 from nallar/master

Handle getAvailablePlayerDat when overworld is not loaded. Fixes #1276
Update to Forge 7.8.1.738
Custom entities isSpawnable() via Bukkit API. Ref #1272

For modded entities added to the Bukkit EntityType wrapper with custom
MCPC+ wrapper classes, set 'independent' to true, so isSpawnable() is true.
Attempt at spawning mod entities via Bukkit API. Ref #1272