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/execution/FactoryExecution.ts

@@ -51,11 +51,11 @@ export class FactoryExecution implements Execution {
         this.game.config().trainStationMaxRange(),
         [UnitType.City, UnitType.Port, UnitType.Factory],
       );
-      // Use different seeds or trains will spawn simultaneously
-      let seed = 0;
+
+      this.game.addExecution(new TrainStationExecution(this.factory, true));
       for (const { unit } of structures) {
         if (!unit.hasTrainStation()) {
-          this.game.addExecution(new TrainStationExecution(unit, ++seed));
+          this.game.addExecution(new TrainStationExecution(unit));
         }
       }
     }