need a selection for edges and a selection for nodes according to occurences

[ungentilgarcon]

so that we can set min/max values for each and filter graph regarding this (get rid of graph centers and decide to show/hide small links)

[ungentilgarcon]

Actually it is done in better time handling, please merge

[ungentilgarcon]

though this version doesn't take into account end dates, it would be easy to add a toogleable switch between time formats (really 2 different options, according to projects, both can be needed, even simultaneously).
BETTER: it could be added to the node/edge field as a "datestyle" field, being either set to value "w_end"/"no_end" changing the parsing style, which is actually the perfect fit (with a default being the current one)