Consider showing last update from github date & time in the ui

[nezda]

Since this tool doesn't push updates from github it would be useful to show the date & time of the last load of the data from github in the ui.

[wired4code]

Not closing this issue just yet, because we may implement a date/time of last fetch. But for now, an update button has been added so users can fetch any new data w/o reloading the entire page, i.e., application.