Add support for multiple Elite:Dangerous accounts

Request EDDI be able to discern which Elite Dangerous account is logged in and provide separate configurations for multiple accounts (support for EDSM, Materials, etc.)

Right now, when I switch between multiple Elite accounts I have to remember to reconfig EDDI for the correct account before I log in or I end up with inaccurate information both locally and being uploaded to EDSM (I actually had to have EDSM delete one of my accounts so I could recreate it and reupload the correct information - my fault obviously, but multiple account support would have prevented my error). And I have to replace the materials .json file with a "zeroed out quantities" materials .json file when switching accounts or the only things that are updated are those materials I have, not those I don't have (which I'm betting is a Frontier thing - they probably don't send zero quantity information).

EDMC (as an example) is able to switch accounts on-the-fly and remembers different logons and API's for the various accounts. Can EDDI be written at some point to do the same?