0.9.9d3 changelist (beta branch update)

[list] [*]Reworked enemy type distribution: - Enemy compositions are now more varied - Smoother difficulty progression across a level - Rooms will now occasionally contain swarms of weaker enemies [*]All level pickups now use dynamic pickup selection introduced in 0.9.9d2 [*]Adjusted shield/ammo pickup spawning to be more consistent [*]Adjusted level fog and lighting [*]Increased Bladder Mine fragment turn rate [*]Increased Killjet size [*]Ionites can now spawn in underwater areas [*]Increased enemy weapon drop rate [*]Increased secret room weapon spawn rate [*]Fixed mine camera rotation in some cases not aligning with room gravity [/list]