Enforce local variables to be local/global

__process_positional_parameters():
  Make sure all the variables and array used within are local or
  global depending on the declaration (keeping our environment clean).
Cleanup and fix command/binary detection functions

__check_missing_programs():
  Fixed antiquated use of old variables to determine whether an
  operation was called.  We now check the $operations[@] array when
  necessary.

  Instead of setting variables that hold the searched-for
  command/binary, each command/binary is stored into a local function
  for use throughout the script.

  As a result, this fixes the band-aid where auCDtect and SoX were
  called directly.  Now, they are called through their respective local
  functions.

  Overall refactoring and simplification as well.

__display_missing_commands_header():
  Removed this function as it's only used once and it's very small.