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.
Wouldn't it be better, rather than using a comment, to add something like:
```
val avgTripsPerWeek = 42
val monthsPerYear = 12
```
and use these in the calculation?