Added work-around language to package ignores for SVN.

It is possible to keep SVN (and most other source control systems) happy with the packages directory, without having the friction of a bunch of pending packages blocking the view of actual changes.

This is achieved based on the assumption that all packages that are downloaded and stored in this directory follow the "[package name][version]" convention. And that NuGet versions follow semantic versioning, which always has some numbers.

I adjusted the language to reflect how to make using package restore in conjunction with SVN easier.