In the calculation of y_start,
when 'column height max' was large it caused
nmin.Y + max_height > nmax.Y - max_height
Now, in this situation y_start is set to the
midpoint between nmin.Y and nmax.Y
Limit y0 and y1 to between nmin.Y and nmax.Y,
otherwise index calculation, which has no checks for limits,
places them at unwanted locations in the voxelmanip
Modders are now able to select the range of ore column height,
and the midpoint at which they 'grow' starting from.
This commit adds three new parameters for the 'sheet' ore type:
column_height_min, column_height_max, and column_midpoint_factor.
clust_size is now deprecated for this ore type.
NodeResolver name lists now belong to the NodeResolver object instead of
the associated NodeDefManager. In addition to minimizing unnecessary
abstraction and overhead, this move permits NodeResolvers to look up nodes
that they had previously set pending for resolution. So far, this
functionality has been used in the case of schematics for
serialization/deserialization.
