Don't use hardcoded unlock levels for Blast Mining
Fix Blast Mining and change its behavior slightly

Fixed bug where Blast Minings ability "Demolition Expert" would not
work with certain CB versions. DanageCause.BLOCK_EXPLOSION was not
passed, ENTITY_EXPLOSION was used instead.

Changed behavior of the Blast Mining ability "Demolition Expert"; now
only decreases damage for the ability user and for Blast Mining
explosions.