feat: connect Human-GEM with more measured metabolites in human cell

[hongzhonglu]

As recorded in https://hmdb.ca/statistics#metabolite-statistics, there are 18,609 detected and quantified metabolites for human cell while in current Human-GEM, there are only about 8458 metabolites, thus it is essential to develop a generic pipeline to add new reactions based on the metabolomics studies so that Human-GEM can better represent the human metabolic activities.

[haowang-bioinfo]

@hongzhonglu thanks for posting this interesting issue. Look forward to a more detail plan for implementation.