We now successfully send outgoing mails with attachments.

  Closes #101.
  Simple test-cases.
  Operate on all arguments.
  Added.
  Show what the script did.
  Cleanup the auto-generated files.
  Remove padding on the message-flags.

  This was only used for the $FLAG expansion in the
 index_format lua-string.  Do the padding there instead.
  Document our data-extraction from the text/plain part.

  Partly because I suspect the code is wrong, even though it
 does indeed work.  Partly for the benefit of other developers.
  Added/updated comments for  CMessage::add_attachments_to_mail()

  Because it is both new and complex.
  Minor comment updates.
  Mention the debug-target.
  Added more assert() statements.

  Just for sanity.
  Avoid segfault in empty MIME-sections.

  I have a weird mail that has an empty text/plain segment.
 Not sure how valid it is, but this fixes it to not-crash
 anyway.
  Updates to the compose() primitive.

  1. If there is no recipient entered, then cancel.
  2. If the subject is empty, use a sane default.
  Removed CLua::call_function().

  This is virtually identical to CLua::execute(), so we've updated
 the code to use that instead.
  Moved code from main.cc into lumail.{cc h}

  This neatens our structure, and simplifies the main.cc file.

  This closes #104
  Fixed typo in comment.
  Updated the ignored patterns.
  Commit the UTF-8 conversion code from @trou.

  This looks good and should go in CMessage.
  Spell-check comments + strings.