Match language space of ETCS for M_AXLELOAD

@coordination.CO @coordination.IS Siemens pointed out that the ETCS spec is able to express more than railML with M_AXLELOAD. In particular the issue is that with the current 3.3 modelling one can express that a speed profile applies to train with an axle load exceeding a certain value. ETCS baseline 2 however allows specifying the special value 126 which indicates that it applies to train exceeding 40t while it also allows specifying the value 40t which implies that it applies for trains of 40t and above.

Potential solutions:

• introduce a choice that allows specifying an exceedsValue or a statement that it is higher than 40t
• rename the attribute to exceedsOrEqualsAxleLoad and introduce a flag that indicates if it is meant to be read as exceeds only
• introduce a choice that allows specifying in general if the enclosing speed profile applies for trains that exceed the given axle load or exceed or equal the given axle load.

all 3 have drawbacks, and all 3 will not lead to a point where the etcs spec exacly matches the railML language space.