Removed obsolete scripts tnl-bindir and tnl-compile and update quickstart's Makefile

- The concept of tnl-bindir is completely useless - it was intended for
  checking if the user configured their $PATH, but the user had to
  already configure  $PATH  in order to use the script.
- The tnl-compile script was used in the quickstart-generated Makefile,
  but gave obsolete output. Moreover, the script approach is inflexible
  and does not provide any benefits compared to hard-coding flags
  directly in the Makefile.