merge r3017, r3018, r3019, r3020, r3021, r3022, r3023, r3196:

merge r3017, r3018, r3019, r3020, r3021, r3022, r3023, r3196:

cache management fixes:

*) separate cache loader process
*) use real file cache length, this fixes cache size counting for responses
   without "Content-Length" header and 304 responses.