Discard files, just use a cache
Context
When loading data from the Web dynamically we can use plain graph.parse() method. Downloading files onto disk explicitly is not strictly necessary for the iolanta browser experience. We'll get back to that when we start editing Linked Data.
Decision
shelve the graph, load data into it. This is enough for an MVP.
Consequences
Get into reproducibility and file-based LD repos later.