Make direction markings on belts, pipes more visible especially in planning mode

It is difficult to see the direction of pipes and belts, especially in planning mode.
Suggestion:
- add visible arrows during planning mode
- increase contrast of the direction markings when build.

Yess! The arrows on the planning mode are so hard to see especially on smaller pipe segments.

Increasing the max zoom level would also help. It is really hard to see what's going on in tight spaces around refineries.