refactoring for dynamic flag encoders

There are two tests failing, Monaco.foot and Monaco.bike. Those tests were misconfigured to use FOOT and BIKE in the test, but Graphhopper instantiated a default CAR encoder for prepare. So the result might be correct.

The problem with the encoder für non-CH prepare was solved by using the first encoder from the manager.

Fixes #66. Changes in many places, please check well before merging.