Merge branch '188_refining_generator' of ssh://gitlab.aicrowd.com/flatland/flatland into 188_refining_generator

Merge branch '188_refining_generator' of ssh://gitlab.aicrowd.com/flatland/flatland into 188_refining_generator

Merge branch '188_refining_generator' of ssh://gitlab.aicrowd.com/flatland/flatland into 188_refining_generator

Merge branch '188_refining_generator' of ssh://gitlab.aicrowd.com/flatland/flatland into 188_refining_generator

now generating inner and outer connections points. Inner points used to set tracks of train station. Outer ones used for inter-city connection

changed behavior of fix transition. If only one inbound connection is found to empty cell, let cell be empty and instead fix the incoming line to a dead end in seperate step

removed possibility of more than two connection direction to and from the cities. In this manner we procude nicer and more realistic city infrastructures

added city boarder to as forbidden zone for inner city connection. This strictly seperates inner from outer connections. should help us to get nicer infrastructures.

helper methods for valid directions

See merge request flatland/flatland!207