Search for missing power line support features

[gaben]

Problem

The power lines are sometimes drawn from low quality satellite imagery and support features can be easily missed.

Proposed solution

Add a java validator test to sort these issues out. It works as following:

• an average node distance calculated for the whole way (line or minor_line)
• for above-average segment lengths, a warning message created where both nodes highlighted to make manual checks faster

Way requirements to lower false positives:

• the way has to have at least 5 nodes
• maximum node distance is 2x of the average

In my testing, they give good results.

Usage

Run the validator, as usual, an extra warning appears if the issue detected.