Import Base64-encoded image data to Asset

Is your feature request related to a problem? Please describe.
I am working on a project to import characters from Chummer5a. Getting the data works fine so far but I would like to have the option to get the images provided by Chummer5a as URL handeled by MT. Or as Phergus put it: "What is missing on our end is the code to grab the image given that URL (or the Base64 data) and then cache it locally like the normal image assets MT uses. Not a huge deal, just someone needs to get a chance to do the work."

Describe the solution you'd like
Code to grab the image and then cache it locally like the normal image assets MT uses.

Additional context
See discord -> #support4dev 15.05.19

[Phergus]

Note that the Universal VTT import added code to read in Base64-encoded image data and turn that into an asset so much of the work is done.