Modular API for Telemetry

[slyubomirsky]

We have a basic telemetry system included in the dashboard now but it makes extensive assumptions about the system the dashboard runs on (e.g., using sensors and nvidia-smi to gather data and parsing records of the outputs of these commands). In the long term, we should separate the source of telemetry data and its parsing mechanism from the dashboard infrastructure and make it possible for users to write their own data-gathering and parsing files that can be specified by configuration.

@AD1024 this will be a longer-term goal