Add multiple private key support #1
Description
Users should be able to go into the file menu and select and option that brings up a window for switching to another key. For example, the application might be set for GitHub, but you want to switch the key to use it for Twitter. The same popup when will have labels for the keys and buttons to manage the keys.
As an extra, perhaps right-clicking on the LCD panel can bring up a quick menu for switching keys easily.