added a level generator that chooses randomly between inner generators
Revert "added a level generator that chooses randomly between inner generators"

This reverts commit b48468e0f8c3534c597ffa42b47d3604571d9ea5.
added cave level generator
added level generator that chooses inner generators based on a property map
map selected generator now uses floats as borders
added temporary cave floor and wall textures.
these need to change, this does not look like a cave at all :D
added cave factory
parameter -nomusic now loads music as streamed media. lags while starting and stopping music, but loads faster. debug ftw!
debugged cave generator a bit, need to continue @ another machine!