Sqrat changes, Spawner improvements, FileSystem changes, Updatable changes too!

Sqrat was modified to allow for a getter/setter pair with const methods take take non-const parameters by value. This was to allow for the Updatable change to take place. Updatable::update() now takes dt by value instead of const reference.

FileySystem now proxies more functions from PhysFS so it can be used instead.

Spawners now use the sleep/wake mechanism to spawn stuff. If they are deactivated then they won't wake up anymore until the stage is started from the beginning.