T1743
I've coded and deployed a simple back-end engine that will accept user submission of token icons. The icons are then manually reviewed and approved. Approval is by clicking on a button in a Telegram channel, so can be quite quick without too much extra work.
This diff implements user tools for creating and uploading a customized token icon. For now, only creating the icon on token creation is supported. In the future I will add a way for users to upload an icon for a previously created token.
While the diff seems like a complicated change, most of the code comes from previous production mint.bitcoin.com code, available from https://github.com/bitcoin-com/mint