core: add GLOTT loading gauge type

[eckter]

No description provided.

[codecov]

Codecov Report

Merging #5159 (35fb15d) into dev (5da16c9) will increase coverage by 0.00%.
The diff coverage is 50.00%.

@@            Coverage Diff            @@
##                dev    #5159   +/-   ##
=========================================
  Coverage     18.55%   18.55%           
  Complexity     2466     2466           
=========================================
  Files           859      859           
  Lines        106263   106265    +2     
  Branches       2499     2499           
=========================================
+ Hits          19714    19715    +1     
- Misses        85182    85183    +1     
  Partials       1367     1367           

Flag	Coverage Δ
core	79.18% <50.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...ljson/schema/rollingstock/RJSLoadingGaugeType.java	100.00% <100.00%> (ø)
...tion/tracks/undirected/UndirectedInfraBuilder.java	86.01% <0.00%> (-0.31%)	⬇️

[multun]

I'm a bit hesitant: the code change is fine, but I cannot find any reference to GLOTT online. I'm worried it might be some kind of weird special case. No knowing what that is also prevents us from adding a correct compatibility list.

EDIT: found it, it's for trams