Add Origins, HttpInterface, and basic Discord support

[linc]

See: https://nitroporter.org/domain.html#domain-diagram

• Add Origin as a Package type
• Add pull command to retrieve data from an Origin
• Add Discord as inaugural Origin package (pull -> raw data from origin)
• Add Discord as Source package & update docs
• Add dependency on symfony/http-cllient
• Add ConnectionManager compatibility with Symfony ClientHttpInterface
• Add Https as a Storage type & refactor the Storage interface
• Adjust Request() call to use named params
• Simplify a few method signatures to stop passing Migration for no reason
• Deprecate translateDatabaseConfig() (just use direct config names from now on)

Assumes pull will only be sourced from HTTP APIs (Storage\Https) for simplicity today even though that is likely a faulty long-term assumption; it shouldn't be difficult to extend if/when the time comes.

Note that Origin doesn't use Migration, so it has more property baggage than Source et. al. This may be part of the path to deprecating the Migration object eventually.