Add the option to add dynamically changing data

[xivk]

Add the option to add dynamically changing data to a routerdb. This should be:

• Very very fast to read.
• Reasonably fast to update.

[xivk]

This is also planned now:

http://docs.itinero.tech/docs/itinero/development/features/2017-11-16-customizable-ch.html