v0.6.4 - Add caching

What's Changed

• Advanced config - Add caching for the API and for the GUI by @stanfrbd in #53

This is to address #52

• Add default cache of 30 min for the GUI
• Add default cache of 1 day for the API
• configurable using the gui_cache_timeout and api_cache_timeout variables in secrets.json or
• configurable using the GUI_CACHE_TIMEOUT and API_CACHE_TIMEOUT environment variables
• To ignore cache for the API: add "ignore_cache": true in the query (data section) - documented in the wiki
• All timeouts are defined in seconds
• Other: add a funny 413 page

Full Changelog: v0.6.3...v0.6.4