Multi-archive support broken by async loader

[fire-eggs]

The code suggests that multiple archives can be loaded, and then navigate between them. E.g. Alt+Home, Alt+End, Alt+PageDown, Alt+PageUp.

However, Alt+Home / Alt+End seem to be non-functional.

1. Using file browser, select multiple ZIPs to load.
2. Page up/down to nav within first archive.
3. Alt+PageDown to go to second archive; page down a few times.
4. Alt+Home should go to beginning of first archive.

Step 4 goes to beginning of 2d archive.

[fire-eggs]

The async loader only loads files[0] "in the background".

Needs to load the remaining images from files[0], and the remaining archives, in the background.

Not quite sure how to deal with a scenario:

1. User loads multiple archives
2. Async is loading in the background
3. User uses Alt+End (or whatever) to go to the end of the last archive, which isn't finished loading yet.

Consider bailing on the async loader if more than one archive loaded?