The GUI now has a snapshot feature. The record button opens a popup
window, which contains the different recording options.

The cog icon now opens a scrollable list of all of the registered
configurations, both local and remote. This window is created
dynamically each time the cog icon is clicked, so it now includes all of the
configurations that were available as the window was created.

Statistics image is now reset when GUI mode is changed. Removed
n-samples mode (too slow, requires better algorithm). Resetting
the image mostly addresses this use case.