various experiments around gexf parsing: take into account declared atts, trace comments for parseCustom, declarable @cluster_index equivalent, and separate function in sigma_tools for using stock gexf parser (unconnected now)

flags: systematize handling (set in initial setup, cancelSelection, greyEverything, used as params in rendering), rationalize forceLabel, rename customAttrs.neighbors to highlight ; cluster highlight: on click in legend, highlight like neighbors but once ; deselect: background click to deselect is optional

(precomputing once common color/size properties for FillGraph and add1Elem -- and therefore for rendering)

cf. github.com/ISCPIF/gargantext/commit/2e4037c

cursor positioning, neigbors only if not hidden, wait timer for expensive dropEdge loop, classic debouncing, add1Elem for edges

1) fixed logic where same side neighboors where computed several times (=> pass them as argument) 2) renamed updateLeftPanel to clearer updateRelatedNodesPanel 3) passed part of the color switching mecanisms to renderers, based on flags 4) adjust some css and remove some debug comments

Redrawing just the actives (eg selection neighbors) is possible in the canvas context of hover layer and is 140 x faster than full redraw

remove some re-rendering directives (prevent double work in cases when it's going to be done in the next function calls)