Implementation of classes BSplCLib_Cache and BSplSLib_Cache is revised:
- Common functionality dealing with spans along one parametric direction is separated to new struct BSplCLib_CacheParams
- Empty constructors are removed; copying is prohibited
- Code reconsidering degree and other parameters on each call to BuildCache() is eliminated; curve parameters must be the same in constructor and all calls to BuildCache()
- Extra call to BuildCache() from constructor is eliminated
