Feature/plugin factory improvements

See merge request visnow.org/VisNow!219

cleanup of transparency GUI and corresponding parameters/widgets, in...

See merge request visnow.org/VisNow!217

Fixed mouse behaviour in viewer3d

Closes #224

See merge request visnow.org/VisNow!218

cleanup of transparency GUI and corresponding parameters/widgets, in particular float subrange slider

feature/Java9

See merge request visnow.org/VisNow!215

Streamlines transparency added.

See merge request visnow.org/VisNow!216

Streamlines transparency added. To show, use read VisNow field: bluntfin.vnf -> stationary flow visualization -> Viewer3d and in streamlines:datamap set transparency-> density. Play with the transparency settings to show streamlines in high density (shockwawe) area.