Add support for LinkedIn company

Thanks.

The file in #3 would need to be converted to a patch (please search the Internet for explanation if you don't know how).

We can't just remove the possibility of 'in' pages. I can see 3 options:

1. A separate entry for every type of page - but could be quite a lot: school, university, ....
2. Make the base part be without any 'company' or 'in', and put that into the 'username'. In this case we would need an update hook to change existing sites.
3. Add a new GUI field to choose the type from a dropdown list. This is the most complex to code.