Use strpos to check our current page rather than an exact match

This allows for various query parameters to be included in a URL.

But. Now that I'm writing this commit message, I think we should probably check for a specific query parameter instead. Then we don't have to work around ordering at all.
Use DOCUMENT_URI rather than REQUEST_URI for view matching

This forces us to explicitly check for the display parameter rather than including that in part of our comparison.
Introduce sorting functions for the Networks display page

Allows for:
* Sort network by ID, asc or desc
* Sort network by domain, asc or desc

Defaults to network by ID, ascending. Additional logic and functionality will be added shortly.
Temporarily disable sort by network_name
Order results based on the orderby and order parameters

Makes use of the usort helper functions that we have setup for ordering results as they are prepared.
Move the network_name lookup to prepare_items() for sorting purposes

This will allow us to sort the items as they are prepared rather than looking the network_name up for each item as it is displayed.
Add support for sorting by network name in the Networks list table