ICB-DCM/PEtab: PEtab v0.0.1

Data format: Update format and documentation with respect to data and parameter scales (#169) Define YAML schema for grouping PEtab files, also allowing for more complex combinations of files (#183) Library: Refactor library. Reorganize petab.core functions. Fix visualization w/o condition names #142 Extend validator Removed deprecated functions petab.Problem.get_constant_parameters and petab.sbml.constant_species_to_parameters Minor fixes and extension