Import configuration from URL

[fxnn]

Setting up a configuration for many logfiles including expressive summaries is a hard piece of work to do, therefore, users will want to share pieces of configuration.

To facilitate sharing, we should make it as easy as possible. Therefore, one should be able to import configuration from an URL. Except for the remote location, everything should work as described in #6.

Supported protocols should be HTTP and HTTPS for the beginning. For faster execution, gowatch should cache the imported files between invocations. We should keep in mind that some users will want to use gowatch in an offline mode; we could support this by downloading once and never again -- maybe just by using the cache.