= update_app_version remodel =

The current app version model started off simple
but has become a complex kludge.
This is a proposal for a new design.

Directory structure:
{{{
apps/
  appname1/
    windows_intelx86/
      1.0/
        (files)
      1.1/
        (files)
      1.1_cuda/
        (files>
      1.1_opencl/
         (files)
    i686-apple-darwin/
      1.0/
        (files)
}}}

The version directories have names of the form VERSION or VERSION_PLANCLASS.
The contents of a particular directory are:

 * application files
 * signature files (FILENAME.sig)
 * a "version description file", version.xml

The structure of version.xml is:

{{{
<version>
  <file>
    <physical_name>PNAME</physical_name>
    [ <logical_name>LNAME</logical_name> ]
    [ <main_program/> ]
    [ <copy_file/> ]
  </file>
  ...
</version>
}}}