Notification About Completed Projects In Cities

**Feature Description:**
Always display "select project" button in the right bottom corner of the screen for any city that finishes building some project even when the production queue for this city is not empty.

Many people might not be involved into micro management thus this feature might be optional and disabled by default.

**Configuration:**
- Always notify about completed projects in cities:
- Yes
- No _[default]_

**Benefits:**
- It's less likely a player is going to forget to use features of completed project right away.
- It's less likely a player is going to forget to change or rearrange production queue according to changes in game.

**Examples:**
- Commercial Hub is completed and player forgets to switch to building Trader or Market.
- Shrine is completed and player forgets to purchase Missionaries.
- Any project is completed and Currency is recently researched but player forgets to put Commercial Hub in production queue.
- Player starts slowly building an army but forgets to build a couple of units in some distant city with not empty production queue.

Start by tracing how city project completion is detected and how the bottom-right "select project" button is displayed, then identify where the optional configuration belongs. The work is done when enabling the setting notifies for completed projects despite a non-empty production queue, while the default setting preserves current behavior.

Written by the indexing model from the issue text.