Brush entity

Brush entities are entities that use a brush model.

To turn a regular brush (usually called a world brush) into a brush entity:
 * 1) Make the brush.
 * 2) Select it. (If you want to have multiple brushes count as a single brush entity, select multiple brushes at once.)
 * 3) Click the toEntity button.

To make a brush entity back into a regular world brush, click the toWorld button.