Default speeds UI listing some non-road assets

[originalfoo]

While testing a PR, I noticed the default speeds panel is including some non-road assets:

Note also the titlebar text too big in German language.

The issue seems to affect several kinds of network; they are not being filtered to only vehicle networks.

Network assets for testing:

• Railway Decorative Networks
• Line Decal Networks
• UK Double Yellow Line
• Striped Networks
• The Railway catenary wires from rail track assets in the Railway collection are also being listed:
  

Some others in the Workshop (I've not tested these but they possibly also have same issue of not being filtered out):

• Airport Lines Pack
• Airport Network Line Pack
• Airport Marking Lines Pack
• Korean Road Color Lane Network

If we can't properly filter we might instead need a blacklist of "things that look like networks but really are not".

Correctly filtered out:

• Pedestrian paths
• Fences
• Power lines
• Ship / Aircraft routes
• Cable car wires
• Castle ruin walls
• Airport runways and taxiways
• Curbs
• Canals
• Pipes
• Flood walls and quays
• Bunch of other weird workshop networks I have

[originalfoo]

Been looking at the segments in Mod Tools scene explorer, noticed following in their .Info (type: NetInfo) property:

• m_vehicleTypes = None is common on assets that should be filtered
  • That also applies to pedestrian-only paths
  • But not bicycle paths (m_vehicleTypes = Bicycle)

In summary, I think a viable filter could be something like:

// pseudo code

private bool CheckCanHaveSpeedLimit(NetInfo info) {
   return info.m_vehicleTypes != None && info.m_vehicleTypes != Bicycle ;
}

Or, alternatively, check that vehicle type can be car, train, tram, monorail, metro and any others I've not thought of.

[originalfoo]

Also, TM:PE scans all networks during loading process at some point, so could likely hook in to that and cache results.

Could possibly also investigate #378 at same time?