Refactor, separate docs from headers, add ru docs

Doxygen kind'a sucks and I need multilanguage documentation, so I did
that. Also, separated massive Math.h file into smaller files.

include/BH/Math/Misc.h

@@ -0,0 +1,17 @@
+#ifndef BH_MATH_MISC_H
+#define BH_MATH_MISC_H
+
+#include "../Common.h"
+
+float BH_Lerpf(float a, float b, float t);
+
+
+
+void BH_Triangle3fBarycentric(const float a[3],
+                              const float b[3],
+                              const float c[3],
+                              const float point[3],
+                              float out[3]);
+
+
+#endif /* BH_MATH_MISC */