runtime: added ability to name threads, TPB scheduler automatically names each block's thread
blocks: WAV file sink's DTOR is not called, so added 'stop' override to force call of WAV file completion routine (fills in total size in RIFF header)
grc: honour order of block paths, print them out on startup, override hier block and pref file path with GRC_HIER_PATH & GRC_PREFS_PATH