use react-router to specify network url in location url

[alx]

Something like http://parasol.deepdetect.com/#data/mnist.csv would be great to specify a network url to load by default.

This data/mnist.csv url parameter could exist in settings network_loader parameter (/networks.json by default), it'd load its default parameters.

If this data/mnist.csv url parameter doesn't exist in settings network_loader parameter (/networks.json by default), the network will be loaded with default global parameters.