Add support for using SQLite as a DB

[lyricnz]

Related to #268

• removes need for docker for local development/execution (once you have the DB file)
• removes need for 3GB docker image
• removes need for cpu + memory required to run postgres in docker

Future work:

• publish the DB image somewhere; Perhaps using Git LFS
• compress?
• read-only?
• automatic bootstrap if DB file not found (download, unpack etc)
• web-based DB file, using range HTTP requests?

[lyricnz]

PR also removes db.get_list_vs_total() which wasn't used anyway

[lyricnz]

Sample releases (from my fork): https://github.com/lyricnz/nbn-upgrade-map/releases

[lyricnz]

So @LukePrior ?

[LukePrior]

Looks good