IDEA-130959 (do not start the progress when headless)
IDEA-130959 (do not start the progress when really headless)
UpdateChecker — use platform timeout defaults (5 sec connection timeout could be not enough even in normal case)
cleanup
cleanup
cleanup, progress indicator nullability
cleanup
cleanup
Use HttpRequests to fix IDEA-131621

checkPluginsHost — don't load twice versions info (we still parse it twice)
ensure that we download plugin under determinate progress
cleanup