Eip micropayments standard for nfts and multi tokens (#4393)

* New submission for EIP proposal Micropayments Standard for NFTs and Multi Tokens

* Added github username to author

* Corrected EIP md file name to eip-###.md

* Tidied up; removed the ignore files

* Made changes to conform to the eip-template.md

* Added FEM link to the discussion-to section in the proposal

* Made the changes suggested by @lightclient

* Added support for shared holders of multi tokens

* In assets folder, changed to include only .sol files

* Added text to proposal to explain how tips help to create a level playing field

* Removed implementation as requested by @axic

* Removed optional Reference Implementation section and added snippet example implementation to help clarify Specification section in response to @MicahZoltu comment.

* Corrected couple of typos as pointed out by @MicahZoltu

* Made the changes requested by @lightclient, such as a more concise abstract

Author: julesl23