Policy for entries for (commercial) service providers

Just to write it down and remember it:

- there should be a link to a page with borg-related information at the provider, preferably https
- there should be a generic, neutral, short description about what the provider is offering
- there should **not** be a "feature list"
- this is something the provider can present (and keep uptodate) at the linked URL
- we don't want a feature competition on our page, nor update lists of features when they change