Petab-ms

Library:

* Fix parameter mapping: include output parameters not present in SBML model
* Fix missing `petab/petab_schema.yaml` in source distribution
* Let get_placeholders return an (ordered) list of placeholders
* Deprecate `petab.problem.from_folder` and related functions
(obsolete after introducing more flexible YAML files for grouping tables
and models)

Data format:

* Introduce observables table instead of SBML assignment rules for defining
observation model (PEtab-dev/PEtab244) (moves observableTransformation and noiseModel
from the measurement table to the observables table)
* Allow initial concentrations / sizes in condition table (PEtab-dev/PEtab238)
* Fixes and clarifications in the format documentation
* Changes in prior columns of the parameter table (PEtab-dev/PEtab222)
* Introduced separate version number of file format, this release being
version 1

Library:

* Adaptations to new file formats
* Various bugfixes and clean-up, especially in visualization and validator
* Parameter mapping changed to include all model parameters and not only
those differing from the ones defined inside the SBML model
* Introduced constants for all field names and string options, replacing
most string literals in the code (PEtab-dev/PEtab228)
* Added unit tests and additional format validation steps
* Optional parallelization of parameter mapping (PEtab-dev/PEtab205)
* Extended documentation (in-source and example Jupyter notebooks)

Bugfix release

* Fix `petablint` error
* Fix minor issues in `petab.visualize`

Data format:
* Update format and documentation with respect to data and parameter scales
(PEtab-dev/PEtab169)
* Define YAML schema for grouping PEtab files, also allowing for more complex
combinations of files (PEtab-dev/PEtab183)

Library:
* Refactor library. Reorganize `petab.core` functions.
* Fix visualization w/o condition names PEtab-dev/PEtab142
* Extend validator
* Removed deprecated functions petab.Problem.get_constant_parameters
and petab.sbml.constant_species_to_parameters
* Minor fixes and extensions