[update] definition of glossary and MG

[apenzk]

Summary

This PR introduces changes to MIP-15, which defines MG and glossary

• clearly introduces the Glossary
• moves the glossary into the wiki: https://github.com/movementlabsxyz/MIP/wiki/glossary
• slightly redefines how MGs work
• provides a first example for the glossary
• Glossary update with terms that we think are relevant.

Reasoning

• Addresses Issue 87
• The MG standard is not used
• A glossary is useful and is also what is commonly used in the space. E.g. https://ethereum.org/en/glossary/
• The glossary should contain ALL terms including the ones on the branches. This implies having it on main only, is not sufficient. Hence the use of the wiki.

review has been addressed