support OpenDRIVE 1.5 features

[namdre]

This is a list of new features that might be relevant or should be checked for 1.5 support
Also see OpenDrive 1.4 support: #6694

• Read OpenDRIVE file referenced in include tag #13686
• header / offset import location offset from OpenDRIVE #10006
• road objects outline (<cornerRoad>, <cornerLocal>) OpenDRIVE: import road object shape outline #13203
• alternative road predecessor/successor definition (elementS, elementDir)
• signal position stuff (implies stopOffset / junction shape), <positionRoad>, <positionInertial> OpenDRIVE: signal positions and junction shape #12803
• virtual junctions, virtual connections question about OpenDRIVE 1.5 feature: virtual junction #7877
• connectionMaster
• new road types (abstract speed limits)
• OpenDRIVE: official support for road object export #12060

There further new features that are probably not relevant (listed here for completeness)

• roadmark stuff (sway, color, explicit blocks) Use OpenDRIVE road markings to derive lane changing permissions #12898