add better storage solution

[t0mdavid-m]

This PR adds a caching solution to the template. Files/Data can be stored using a simple interface (store_file/store_data). Cached data is written to disk and kept track of using a sqlite3 database. Files are stored in a central location and their path is stored as a reference. Python objects are pickled and gzipped, with the exception of dataframes, which are written to parquet.

ToDos:

• Avoid troubles while pickling the FileManager under windows
• Add File Manager Page
• Complete Documentation
• Check if the complete file manager can be moved to this solution without breaking backwards compatibility

[t0mdavid-m]

@Arslan-Siraj