More robust parsing of the HTML table output given by InaSAFE

[vdeparday]

Since the html table given by InaSAFE is variable depending on the impact function and on the extent of the calculation, the wrong data can be parsed and return to the UI.
Waiting for the next InaSAFE version and a json output, a more robust parsing of the html should be done, maybe using a python parsing library like pyparsing or beautifulsoup.

Here is code snippet in question: https://github.com/inasafe/safe-geonode/blob/master/safe_geonode/static/safe/js/safe.js#L173-L176