unclutter window scope of all parse-related and category-related vars + clarify confusion in using the word "reverse"

restored switch in main allowing API graph data input in json + started debugging types/categories + introduced the more generic variants of getUrlParam and prepareNodesRenderingProperties we did in comex2

All these advances from politoscope prototype will be useful for the port and general refactoring:
  - removed legacy cortext localdb
  - new 'attrs to bins' logic (cf. scanClusters in parsing)
  - new 'attrs to colors' logic
  - new alt_colors rendering
  - new histogram variant: *daily* histograms
  - ! new simpler twitterAPI (directly with twitter's endpoints) !
  - useful debug logs for db.json loading and parseCustom
  - prepared parseCustom 'types' refactoring
  - getCurrentType function

cf. https://github.com/jacomyal/sigma.js/issues/340

factor in binning we had for legends to a much earlier stage in parsing, thus creating value facets with reverse index accessed via TW.Clusters.type.facet[facetvalue].nids

Changes color rendering to black :/
This reverts commit 15f1f819.

This reverts commit d76dc7f5.

cf. https://github.com/jacomyal/sigma.js/issues/340