Improvements to config handling and RAW audio

Handling of config values now more strict. Each custom features checks if
the config values passed to them are valid or need to be obligatorily
initialized. Non supported fileds now removed from config files.

HCopy_UP now checks if tools instaled by checking if voicebox is available

Improved support for RAW format in readaudio.m and possibility of downsampling

These changes make the tools compatible with DIRHA-sim corpora (currently
unpublished).
complete_defaults.m checks for valid arguments in custom features