WIP: Update glue for WebAPI 2.12.x

[actualben]

• Added boolean option source_cache to multiconfig.py (defaulting to true)
• Added get_info function to webapi.py which polls the /info endpoint (without requiring authentication)
• In glue.py's glue_it we use get_info to pass the webapi_version to ensure_webapi_source this passes it to create_source and update_source
• Updated the 3 aforementioned source management functions to only configure is_cache_enabled on WebAPI >=2.12.0
• Added semver.py module to handle version comparisons

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Keeping an eye on these issues:

• https://github.com/OHDSI/WebAPI/issues/2034
• https://github.com/OHDSI/WebAPI/issues/2131
• https://github.com/OHDSI/WebAPI/issues/2154

[actualben]

(This is WIP until it gets a test-run)