[Feature] Allow multiple save-file databases for swapping between multiple accounts

[fribbels]

Motivation

Currently the optimizer only supports one loaded save database at a time. This functionality is OK for now but can be annoying for people with multiple accounts.

Objective

Goal: Allow for swapping between multiple account setups on the Import / Save tab. Also revisit the Save / Load tabs on that page to consolidate the Save / Load buttons together when selecting a DB profile.