awget.in: Move global configuration to `config.scm.in'

* awget/config.scm.in: New file.
* awget/awget.in: Move global configuration of directories and
  files to `config.scm.in'.
* awget/Makefile.am (awget_DATA): Add `config.scm'.
  (.in): New target.
  (CLEANFILES): Add `config.scm'.