New spells, more tiles customization

Version 0.9.9.1 brings following features:

- New spell: Silence Field - disables all enemy spell-casting in a radius

- New spell: Venom Surge - infects an enemy with poison that explodes on death, spreading toxins to nearby foes

- Tiles customization! Do not like factory tiles? No problem replace them by your beloved ones. This time added: Interactive tiles