The kegg2bionetwork tests required web connection to check DTD validity.
refactor Kegg2BioNetwork to split the DocumentFactory creation
Creates a Mock to return a DocumentFactory without DTD checking for tests

now handle GSAM files w/ carbon indexes

a function that takes a string and output a double can be passed to add flexibility in weight import

77 s vs 1200 s to read Recon3D !

Example : getReaction(id) instead of getReactionsView().get(id)
and containsReaction(id) instead of getReactionsView().containsId(id)

avoid latency during reaction graph build and traversal due to over-density