Custom world generation/surface rule


 * : Type of the surface rule, one of:,  ,  , or  . See below of extra fields for each type.
 * If is   (used in badlands), no extra fields.
 * If is   (places the specified block), extra fields are as follows :
 * : The block to use.
 * If is   (attempts to apply surface rules in order, and only the first successful surface rule is applied), extra fields are as follows :
 * : (Required, but can be empty) List of surface rules.
 * : A surface rule.
 * If is   (applies surface rules if the condition is met), extra fields are as follows :
 * : A surface rule condition.
 * : A surface rule.
 * : A surface rule condition.
 * : A surface rule.
 * : A surface rule.