Unsupported quantity `LateralDischarge`

[jeroen-deltares]

Describe the bug
LateralDischarge, lateraldischarge1d and lateraldischarge2d are quantities that are supported in the kernel but not yet by the converter.
Refer to the user manual on Lateral Discharge quantities:
https://content.oss.deltares.nl/delft3dfm2d3d/D-Flow_FM_User_Manual.pdf
section: C.6.2.2 Lateral discharge definitions

To Reproduce
p:\dflowfm\users\veenstra\extforce-convert\dflowfm3d_dwaq-grevelingen-j19_6-v2b\computations\hist\jaarsom_2017\ run this model and it will throw validationerrors on the LateralDischarges.

Expected behavior
The LateralDischarge quantity should end up under a [Lateral] header in the new ext force file.