move d3 force calculations to webworkers

[scsirdx]

Just an idea for now.
Research should be done about current state of webworkers support (esp. about that bugs in chrome). If all is good, the d3 heavylifting should be done in webworkers.

[ffaerber]

i dont think this is useful for the bubble chart.
the loading and initalisation of bubbles can be optimised in d3.

[scsirdx]

It's not about math optimisation, it's about moving heavy stuff out of main js loop to make UI more responsive. This is not a problem for now, but it can pop up after adding some additional UI elements (like charts, etc.)
So this ticket is more like "one of the ways to make UI more responsive". It's a lowest priority, just one of ideas for optimisation.