hazard curve viewer - extended

[Ben Wyss]

We have now created a basic hazard viewer using leaflet/utfgrids/d3.js. This application is able to plot a single hazard curve. This bug is aims to extend the app so that it is able to render multiple hazard curves on a single plot.
The utfgrid first need to be loaded with multiple curves and metadata to discriminate the curves from each other.
The application will then need to provide the user with an interface used to select the curves to be plotted in the d3 chart.
The d3.js chart will need to be expended to handle multiple charts and interactivity.