Another mostly technical update: lava spells for sandbox and technical stuff for future mod support.
- Added lava source, sink and globe spells for use in the sandbox mode.
- Switched to physfs library for reading/writing game files. Building editor now saves to %APPDATA%\buildings\ folder.
- Optimized file checks (like reloading shaders/textures/scripts).
- Switched to Visual C++ 2013. No runtime installation necessary, so ignore this.
- Changed button style in the main menu.