Dataset IDs need to be URL-encoded

[kring]

For example, try this search:
http://magda-dev.terria.io/search?q=ESTA+EMERGENCY+MARKERS

And then click on the first result. It goes to here, which is invalid:
http://magda-dev.terria.io/dataset/http://data-esta000.opendata.arcgis.com/datasets/df294d0463b44efd85f5e66f90825451_0

But this works fine:
http://magda-dev.terria.io/dataset/http%3A%2F%2Fdata-esta000.opendata.arcgis.com%2Fdatasets%2Fdf294d0463b44efd85f5e66f90825451_0

It's a little awkward to use a URL as an ID, but that's what this data.json source is doing so we have to deal with it. In any case, there are other reasons we should be URL-encoding the id. encodeURIComponent(id) will do the trick.