Framework improvements

This is a follow-up of !550 (closed) which intends to improve the framework.

Included improvements:

  • fix typos in names
  • add comments
  • rename outputFormat to outputConfig in decoder.c
  • add error return checks in decoder.c
  • remove hrtfCRendReaderEnabled and hrtfCRendFileName leftovers
  • remove obsolete data type conversion in ivas_fb_mixer_cross_fading()
  • add const to ROM tables
  • define function ivas_hrtf_init() as global instead of twice as local ones