Factory spawns trains (#1408)

## Description:

- Change trains so it spawns from factories only
- Increase train frequency as they will now spawn from a single
structure.
- Factory will spawn more trains depending on its level
- Fix port to connect to nearby railroads
- Add factory description

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

## Please put your Discord username so you can be contacted if a bug or
regression is found:

IngloriousTom

---------

Co-authored-by: Tom Rouillard <trouilla@mathworks.com>
Co-authored-by: evanpelle <evanpelle@gmail.com>

src/core/configuration/DefaultConfig.ts

@@ -326,7 +326,7 @@ export class DefaultConfig implements Config {
     return this._gameConfig.infiniteTroops;
   }
   trainSpawnRate(numberOfStations: number): number {
-    return Math.min(1400, Math.round(70 * Math.pow(numberOfStations, 0.8)));
+    return Math.min(1400, Math.round(20 * Math.pow(numberOfStations, 0.5)));
   }
   trainGold(): Gold {
     return BigInt(10_000);