Add local caching

[vavalomi]

!!! WORK-IN-PROGRESS

These changes add support for local caching for the datasets as well as catalogs.

• new, general-purpose, and transparent caching mechanism added via -datachache- command.
• some of the existing approaches of locally stored data (specifically for catalogs) were switched to this new approach.
• TODO: price data as well as latest catalogs are stored in mata matrices, so could be also transitioned to this.
• TODO: no cache expiration procedures have been implemented yet. The only way to refresh currently is to manually delete local files.

TODO: there are parts of the system (within main datalibweb, as well as separate ado files) that may still make direct API calls and therefore not go through caching.

TESTING: as large parts of the code affecting logic were modified, testing needs to be done to identify broken workflows.