Fixes graph view node identifiers when node id strings are exotic

Scalding runtime generates MR jobs with names which contain various symbols. These symbols crept into `id` attributes of the `circle` svg elements in the graph view and broke click behavior.

This patch migrates node id strings from the `id` attr to a new `data-node-id` attr and updates css selectors to make use of the new attr.

Tested successfully in demo mode with updated demo data.