[FIX] Multiple parameters for route_v8

[maciej-wichowski]

1. Improve encode_parameters method, so it processes dict parameters correctly. Here API expects multi-level dict to be expressed as key[sub1]=val1&key[sub2]=val2. The method supports only one level sub-dict, which as far as I know, should be enough.
2. Fix route_v8 - avoid, exclude and truck parameters were not fully supported.

Fixes #83