Add missing / not implemented default getSettings values

[mcspr]

• update thingspeak, api, scheduler to use header defined default values
• fix scheduler defaults to use the same values as webui presets when creating a new schedule
• fix generateapi() in webui to trigger only when apiKey getSetting output is empty (API_KEY or apiKey missing or empty string)
• minor fix from WebUI fix change detection of input elements #1986 to the originals setter to handle checkboxes output

mostly from #1986, avoid mixing originals webui problem with these