Allow files to be requested by URL in /player/

[DevonJames]

Many artifacts will have more than one file, so we need to be able to call a file in the URL so that /player/ knows what to play.
I suggest:
host/application/artifact?file=#
example:
https://alexandria.io/player/fc2a5a?file=1

Note, please use the array ID for the file requested, starting at 0.

(yes i know that for now it will be https://alexandria.io/browser/player/fc2a5a?file=1)

[copernicus-mogley]

There was discussion of using query operators in the URL for handling files, like https://alexandria.io/player/fc2a5a?file=1
This might scale better than using #, as we add more features.