URL for forge packages

[Carnë Draug]

Hi

the current method to get the URL for packages when installing with
the -forge flag is to parse the HTML of the package for the version
and use it to generate a URL to download it. I see two problems with
this:

1. if we are to change the format of the documentation page this will
start failing
2. if we move the packages to another host (as has been discussed
before), it will also fail

While such changes are not planned to happen on OF soon, when they do
it will mean that users using octave versions before the change won't
be able to use the -forge flag. I think to prevent this before becomes
an issie it's a good idea.  I would like to propose to have a simple
text file on octave.org with this info. 1 line with package names and
their URLs would suffice. This would also make the code to get
packages from forge simpler since the parsing would also be simpler.

Any comments?

Carnë