fixes to block IDs

large flowers are defined only by bottom part -> made top part
completely transparent
fixed id numbers for new door types
moved alpha definition up

There might be a problem with variant blocks not getting the correct
alpha value if the json file is parsed top to down. Therefore it is
better to define all values to be inheritted by the variants before
defining the variants itself.
fixed depth shading

There was a bug in depth shading with semi transparent blocks on top.
With the new blending Flowers and other alpha<1.0 stuff doesn't pop out
anymore.
Merge remote-tracking branch 'upstream/master'
Fix for entity rendering X error

The pull request from thewierdnut renderes entities at a X position one
towards west. With this change entities are rendered at correct X
position (at least in my tests).
added id for Piston Extension

ID 34 is the head of a Piston and ID 36 is a technical block describing
all the stuff moved by the Piston. But Í have no idea about a good
color.
Merge pull request #47 from EtlamGit/master

block ID fixes + entity rendering fix + depth shading fix