Custom In-Memory Reader

[crhoover-maxar]

This is a feature request where it would be useful if there was a CustomReader that cached a file in-memory so that every tile request doesn't use I/O and could draw the content from memory instead of the filesystem

[vincentsarago]

@crhoover-maxar do you want to cache only the tiles or the whole file?

[AndrewAnnex]

I'd imagine both would be of interest, but I currently have a similar desire for the whole file