work around broken arch: aany packages conflicting with arch: all ones.  make 2nd argument optional and default to 'r' for open_file

Ensure a sane minimum set of fields in the .dsc and ensure the .dsc version matches the .changes version.

fix is_nmu test for namless changed-by.  use subtree for options.  add logging.  less reject_message truncation.  ensure format in .dsc is 1.0.  don't try to obtain lock in no-action mode

make use of utils.{warn,fubar}.  clean up extraneous \n's in fernanda and natalie.  remove old override code from rhona.