Maintenance of `BeamBridge` class which is dynamic system representation

[bogumilchilinski]

The following problems have to be checked or fixed, in order to ensure the correctness of implemented system:

• [x] checking if a class is executable,

• [x] validation of figures for schemes and real examples,

• [x] validation of reference parameters,

• [x] validation of random parameters,

• [x] validation of description of parameters,

• [x] validation of units.

[amvdek]

The code was checked with the following call:

from dynpy.models.mechanics import BeamBridge
from dynpy.utilities.documents.document import DynSysOverviewReport
DynSysOverviewReport(reported_object=BeamBridge())