JupyterParser: should scan `.ipynb` files

[nokome]

Implement a JupyterParser class which scans the folder for any ipynb files, scan the code cells in those files for any Python import or R library statements, extract a list of package dependencies, and create a SoftwarePackage instance for it.

Should also extract relevant meta-data from the .ipynb files and add it to the SoftwarePackage. There currently isn't any CodeMeta crosswalk for ipynb meta data, https://codemeta.github.io/crosswalk/, maybe we could contribute one.