FMIL: Add structure of new `<ModelStructure>` element for #3267. Also add some `<ModelStructure>` data to `modelDescription_me.xml`.
FMIL: Comment out some intentionally ill-formated log-messages from `fmu2_model.c` to reduce noise in the test log file, for #3267.
FMIL: Begin parsing `<ModeStructure><Outputs>` for #3267, and add in vectors to store referenced variables.

Also fix memory leak temporarily introduced in r5563.
FMIL: Refactor r5586 to apply the same kind of parsing to all four child elements of `<ModelStructure>`, for #3267.
FMIL: Resurrect `fmi2_xml_parse_dependency` (as `fmi2_xml_parse_dependencies`) that was removed in r5562, and adapt it to the new `<ModelStructure>`, for #3267.

Also update the `fmi2_dependency_factor_kind_enu_t` enum according to FMI2.0rc1, add four `fmi2_xml_dependencies_t *` fields to `fmi2_xml_model_structure_t`, and add some dependencies to the XML.
FMIL: Add check that only valid `dependenciesKind` values are used within `InitialUnknowns`, for #3267
FMIL: Uncomment FMI2 `get_outputs` etc. functions and rewrite to export the four lists that exist in the new `<ModelStructure>`, for #3267.
FMIL: Reinstate getting of dependency information from `<ModelStructure>` that was removed in r5561, for #3267. Update the functions to get the new categories of dependencies.

While the dependencies are listed as indices into `<ModelVariables>`, they are still indexed by the index in their corresponding section (`<Outputs>` etc.) Might want to change this.
FMIL: Expose the `ScalarVariable` attributes `previous` and `canHandleMultipleSetPerTimeInstant`, and the `Real` attributes `derivative` and `reinit` to the user, for #3267.

Also change so that `previous` and `derivativeOf` are represented as variable pointers, not indices. Had to temporarily store the indices as ints in the pointers during parsing, since the variable list is not accessible to look up into until it has been constructed.
FMIL: Change handling of `fixed` in `dependenciesKind` list under `InitialUnknowns` from error to warning and correct to `dependent` for #3288.

Also fix a some spelling mistakes.
FMIL: Rename attribute `providesDirectionalDerivatives` to `providesDirectionalDerivative` for #3267 and but check for and warn if the old name is used, for #3288.
FMIL: Disable error exit for `derivative` attribute on non-continuous variable, for #3288.
FMIL: Calculate `numberOfContinuousStates` as the number of derivative variables, for #3267.

The FMI2.0rc1 specification says that `numberOfContinuousStates` can be calculated from the XML, but it does not say how. It also says that the `ModelStructure` derivative information is ignored for cosimulation unless `providesDirectionalDerivative = true`, but hopefully we should still have derivative variables that are marked as such?
FMIL: Remove hardcoded number of states from `fmi2_import_me_test.c` for #3267, since we can provide the number of states again.
FMIL: Count the number of continuous states as the number of elements in the `<ModelStructure><Derivatives>` element, for #3288.
FMIL: Move parsing of `derivative` and `reinit` attributes to after other `Real` attributes for #3267, to avoid segfault that was caused when parsing errors in these attribute left the data structures semiinitialized.

Now, the parsing finishes with an ok status even when a `derivative` attribute gets a malformed value, however.