Network display name

[Nospamas]

Alternative approach to human readable identifiers within the network table this PR:

• Adds a network_display_name column
• Populates it with existing network_names
• Adds a trigger to prevent the existing network_name column being updated

It retains the same changes as from network_key for:

• Adding versionable ORM tables for testing without the new column
• Re-adding the history table to maintain column order
• Adjustments needed for tests to pass