Move caches to dashmap::DashMap

[Gerard Klijs]

Is your feature request related to a problem? Please describe.
Faster cache at the prize of an additional dependency.

Describe the solution you'd like
Use it for everything to keep maintainability good. There are already a lot of features.

Describe alternatives you've considered
Having it as feature, but that increases complexity, especially as it's in a complex integrated piece.

Additional context
See discussion #67