engine: now using hashmap for storing terrain chunks
game: fixed random range function and renamed sound variables
engine: implemented operand-templated modulo function
engine/terrain_object: comments indented correctly
engine/terrain_object: implemented basic underground terrain checking
engine/terrain: comment for draw function fixed
game: terrain initialisation size definition as constexpr
engine/terrain: fixed using 2 map queries for getting chunks
engine/terrain: another hash function for chunk coordinates