ARISTOTLE: Download and display intensity map from the USGS website if available

[ptormene]

I am going to work on producing our own version of the intensity map and the pga map, but for now I am displaying those downloadable from the USGS website.

The get_shakemap_version function is useful in general to retrieve objects from urls formatted such as https://earthquake.usgs.gov/product/shakemap/us7000n7n8/us/1726699735514/download/intensity.jpg, where us7000n7n8 is the USGS id and 1726699735514 is the shakemap version. With that function we can obtain the shakemap version given the USGS id.