Add option to truncate city names beyond a certain length in city banners

**Issue by [chaorace](https://github.com/chaorace)**
_Monday Jan 09, 2017 at 08:36 GMT_
_Originally opened as https://github.com/CQUI-Org/cqui/issues/234_

----

Currently some of the automatic city names are a little ridiculous in length. Technically speaking, you only really need the first 5 or so characters to quickly identify your cities, so I think there's some value in offering an option to truncate the city name as displayed in the city banners. This would be a slider option from a scale of 0 (for no nametags at all) to Never (for full nametags no matter what). I suppose "Never" is going to be an arbitrary value of some kind. I think 20 is a fair maximum value to set "Never" as for starters. I'd leave the default value at "Never" since this seems like the kind of change with a lot of capacity to bug people who've just installed the mod.

[More info](https://www.reddit.com/r/civ/comments/5mqlkl/long_feedback_on_civ6_from_a_longtime_series_fan/)

No files, tests, or entry points are identified in the issue. Start by locating the city-banner UI and the existing mod options or settings screen, then trace how city names are displayed and configured. Done means a configurable truncation range, including hidden and effectively unlimited values, with the requested default preserved.

Written by the indexing model from the issue text.