- fixes after FLD CR:

- fixes after FLD CR:
  * cache API is moved to fld_cache.c;
  * cache is now used both on server and client;

  * fixed name aliasing. There was fld_cache global struct, also there were lots of functions which took fld_cache instance pointr which name was fld_cache;

  * fixed memory leaks in fld_cache_fini(). There was missed releasing of all cached entries;

  * do not translate fld_cache_*() errors to caller on server and client. If some error happens in cache working funtions, we do not care of that.