Merge comments and keywords

[veenstrajelmer]

Is your feature request related to a problem? Please describe.
In the hydrolib.core.dflowfm.mdu.models code, all mdu keywords are defined. The comments and keywords+type+default are defined separately, like so:

HYDROLIB-core/hydrolib/core/dflowfm/mdu/models.py

Lines 45 to 77 in 08b8294

	class General(INIGeneral):
	"""The MDU file's `[General]` section with file meta data."""
	class Comments(INIBasedModel.Comments):
	program: Optional[str] = Field("Program.", alias="program")
	version: Optional[str] = Field(
	"Version number of computational kernel", alias="version"
	)
	filetype: Optional[str] = Field("File type. Do not edit this", alias="fileType")
	fileversion: Optional[str] = Field(
	"File version. Do not edit this.", alias="fileVersion"
	)
	autostart: Optional[str] = Field(
	"Autostart simulation after loading MDU or not (0=no, 1=autostart, 2=autostartstop).",
	alias="autoStart",
	)
	pathsrelativetoparent: Optional[str] = Field(
	"Whether or not (1/0) to resolve file names (e.g. inside the *.ext file) relative to their direct parent, instead of to the toplevel MDU working dir",
	alias="pathsRelativeToParent",
	)
	guiversion: Optional[str] = Field(
	"DeltaShell FM suite version.", alias="guiVersion"
	)
	comments: Comments = Comments()
	_header: Literal["General"] = "General"
	program: str = Field("D-Flow FM", alias="program")
	version: str = Field("1.2.94.66079M", alias="version")
	filetype: Literal["modelDef"] = Field("modelDef", alias="fileType")
	fileversion: str = Field("1.09", alias="fileVersion")
	autostart: Optional[AutoStartOption] = Field(AutoStartOption.no, alias="autoStart")
	pathsrelativetoparent: bool = Field(False, alias="pathsRelativeToParent")
	guiversion: Optional[str] = Field(None, alias="guiVersion")

Describe the solution you'd like
From a maintenance point of view, it would be convenient to define the comments as part of the keyword, for instance by defining a class based on Field, containing an extra comment property. Furthermore (and alternatively), it would be great if all keywords (including type, default, GA/research status, comment and existing/deprecated status) could be moved to a json/csv file instead of being defined in the code. This would be a first step towards aligning the keywords between kernel/hydrolib-core/GUI.