Ability to select and delete multiple .gcode files in the AstroBox File Manager

[DilankaW]

This was requested by an AstroPrint user. (See original tweet)

I also agree.

There should be a mechanism to select ALL/MULTIPLE .gcode file(s) from the Astrobox File Manager.

[CoDanny]

One feature request per issue, please :)

I have added a new issue for the sorting request #100