Implement Lenses/States for MathHub
We would like to have an infrastructyure quality control in MathHub. The model that seems adequate is the "lenses" model introduced by the connexions project; now OpenStax. The idea is to allow open submission to MathHub and do the quality control later by allowing anyone to define a named "lens", which endorses certain objects as "interesting and (sufficiently) good" and which can be used by users to direct their attention. The important innovation is that lenses are public and can be created, followed, copied & extended by anyone. Communities will usually have their own "quality approved" lens, and lenses can also be used as an "overlay journal" over MathHub.