Updated demo to version 0.9a

Version 0.9a changes:
- Smooth fog of war, due to multiple requests

- Dynamic Water.
- Cataclysm spell to flood your enemies and open a passage through waters. Finally you can play as Moses!
- Tornado spell, which scatters units and removes mist.
- Proper time system, instead of abstract turns. Now every turn models real life hour.
- Night time: every 8 turns out of 24 turns day, from 22:00 to 6:00. Undeads have more defence at night, while units without darkvision have reduced sight.
- Rain, which extinguishes flames in outdoor areas and prevents the use of fire spells, like firestorm and fireball. Units inside rain get -1 to sight.
- Proper wood bridge tile, instead wooden floor.
- Fixed fog sight bug, when cell below or above give units cant be accessed inside fog.
- Fixed bug with invalid empty check, affecting several spells and leading to potential crashes when one creature teleports into another creature.
- Fixed crash hiding drowning unit.