Enhancement: aloevera asm support to select multiple (formatted) imagesets for output to a single .bin file

[CJLove]

This is kind of a special case that mainly applies if using aloevera asm -f bin and not for other output formats. The use case is if you've got multiple formatted imagesets (e.g. sprites images of different size) which you'd like to assemble into a single binary file.

An initial idea would be to allow multiple -select xxx arguments in the aloevera asm command.