More input checks

[mrp089]

Current situation

Closes #70

Release Notes

I added two new features for error checking:

1. JsonWrapper class
   • wrapper around nlohmann::json
   • overwrite [] operator that will throw a detailed error where an input parameter is missing
   • used by all create_... functions in SimulationParameters
   • should catch all errors where required components are not given (e.g. due to spelling)
2. Throw an error in Model::get_block if the block name doesn't exist
   • checks if block exists in Model::has_block
   • deleted get_block error handling in interface as it's not necessary anymore
   • replaced comparisons with nullptr by calling has_block
   • should catch all errors where non-existing block names are used anywhere in the input file

Documentation

Added required Doxygen documentation to new code

Testing

Verified that the examples in #70 and other random manipulations of test cases throw a descriptive error message

Code of Conduct & Contributing Guidelines

• [x] I agree to follow the Code of Conduct and Contributing Guidelines.

[mrp089]

Using inheritance for JsonWrapper makes things a bit easier (updated first comment)