Increased city check distance to work distance * 4

Added limiter to only check for cities within WorkDistance + WorkDistance (Example 6 by default). Anything past this will not have overlapping hexs.
This should greatly improve performance on games with a large number of cities.

Fixed cases where having a selected unit then entering city view would prevent display.
Fixed cases where city limits could persist and did not clear.
Fixed showing city limits on other units that can also found cities such as the Conquistador.
Improved Feature: You can now see overlapping hexs in city view.
Improved Feature: You can now see overlapping hexs from any city. It is no longer limited to your cities.
Improved Feature: This *should* support and work with any unit that can found cities, or increased work distance that is added or changed by a mod. **Untested** Thanks to whoward69 for the code/example.
Added Feature: You can now see city limits for any other civilization, including city-states. Such as viewing the city from a spy.
Added Feature: You can now simply mouse over any hex that contains a city is in to display the limits.

Fixed an issue where CityLimits border would vanish when entering city view.
Made changes that should make the border more reliable to show.

Citys now use a blue border (prevents conflict and distinction to the settlers range)
When highlighted on settler it now shows the range of all your cities as well as any overlapping plots on your settler

Fix for when city has bombardment available (thanks whoward69)
Changed the border to a different type which now uses an orange border