Fix graph translation problem (paths sometimes out of viewbox)

[eputtone]

Workflow graph edges are sometimes hidden outside the viewbox after recent changes. This is fixed by fit: true for svgPanZoom. The previous causes a new problem: fit does not understand stroke width leaving nodes touching the viewport edge partially drawn. This is fixed by zooming out 1% after fitting, but after this hack we do get 1) properly visible graph and 2) get rid of many magic numbers.

Includes also the following:

• increase viewport minimum height 300px -> 400px in cases we have to enable zoom
• wrap svgPanZoom into factory so that we don't get build time warnings (https://www.jvandemo.com/how-to-properly-integrate-non-angularjs-libraries-in-your-angularjs-application/)

[coveralls]

Coverage remained the same at 72.414% when pulling 816da5e on fix-minor-graph-issues into 6910018 on master.