Organizing OGD Core Workflows

[LswaN58]

This is a retroactive proposal, to track a plan that was made and more-or-less put in place via #219.
However, for the sake of good documentation, the original plan is pasted here, and can be followed up on if the need arises.

Sorting out OGD core workflows:

• Each game gets a CI script to run a test export
• Each game gets a README script to generate and commit new readme file.
• Manual export - merges manual and manual events
• Monthly export

Actions

export custom, custom month, last month, last week, yesterday - each action other than custom and custom month calls other actions
gCloud setup - has all the names and keys of alternate BQ projects hardcoded, so not duplicated in other places
generate_readme
OGD_config
set_custom_db - used in manual to support exporting from non-default location
upload_export - action to handle actual loading up to FD server, rather than running copy in the monthly and manual exports.

Left to do

Sort out the tricky gCloud setup stuff. Can't seem to decide if it's nicer to just pass in one source-credential pair, which doesn't really save us much over just using the action directly in each workflow, or to pass everything into the action, which makes everything pretty much perfectly copy-paste and managed by the action, but takes a lot of space.
Could also be smarter about choosing whether to do a certain auth based on selected game. Currently also not really checking the 'alternate data source' stuff to decide if some old thing needs to be set up or not.