Feature/refactor params

This merge request refactors the use of parameters to allow fetching of parameters from the database in addition to only calculating derived parameters (stops buffers, road length, etc.) once so that multiple indicators that need access to these parameters will not be recalculating these values.
p.s. the thing to do for constants like that is to do `final val`. Another thing that is done often is have all caps constants in the companion object.

```scala
object Affordability {
  final val TRIPS_PER_WEEK = 42 // average trips per week
  final val MONTHS_PER_YEAR = 12 // only applicable to earth.
}
```

This is probably overkill for this situation, but just for future reference.