Introduce cmake (min 2.8.12) to StepMania.

tl-dr: view the Build directory to see.

This is intended to replace the project files that we presently maintain
so that only a single set is needed instead of multiples.

The following setups were used for testing:

* Windows 8 and Visual Studio 2013 Desktop Express
* Windows 7 and Visual Studio 2012
* Mac OS X Mavericks and Xcode
* Ubuntu and makefiles
* Fedora 21 and makefiles

All three operating systems can generate projects, compile, link, and
run. Windows and Mac OS X users will find their compiled binary in the
same location as before, but Linux users will be surprised: it goes
straight into the root directory, along with a symlinked GtkModules.so
as appropriate. There is no more need for a manual symlinking step.

Known issues:

* At this time, MinGW likely does not work. Extra time will be needed.
* The WITH_JPEG option may go away, and we'll just always require it.
* Some linux libraries can use the system equivalents, but that is not up yet.

For more information, check out the Build directory.

src/Main.cpp

@@ -0,0 +1,31 @@
+#include "global.h"
+#include "StepMania.h"
+
+int main(int argc, char* argv[]) {
+	return sm_main(argc, argv);
+}
+
+/*
+ * (c) 2014 Jason Felds
+ * All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, and/or sell copies of the Software, and to permit persons to
+ * whom the Software is furnished to do so, provided that the above
+ * copyright notice(s) and this permission notice appear in all copies of
+ * the Software and that both the above copyright notice(s) and this
+ * permission notice appear in supporting documentation.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF
+ * THIRD PARTY RIGHTS. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR HOLDERS
+ * INCLUDED IN THIS NOTICE BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT
+ * OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+ * OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */