* explicitly ignore errors where appropriate
* do not append in a loop
* specify format string in Errorf

Fix path selection choosing a to big step, since the next step
was determined by the moving range and not the actually available
movement tiles.

Fix generating a target for the AI by introducing a dummy action
to support "enemy" target constraints.

Do not allow to declare slow play actions in the client.
Fix the slow action check in the game state.