Rename mob source files to fit CamelCase.

Rename Cavespider.cpp to CaveSpider.cpp

Rename Cavespider.h to CaveSpider.h

Rename Magmacube.cpp to MagmaCube.cpp

Rename Magmacube.h to MagmaCube.h

Rename Zombiepigman.cpp to ZombiePigman.cpp

Rename Zombiepigman.h to ZombiePigman.h
Fixed references to renamed files.
Fixed class capitalization for the cave spider.
Merge pull request #929 from archshift/master

Renamed mob source files to better fit the CamelCase naming style.