get appsettings and merge from hosting web site

Config_example.fs

let localSettings = System.Web.Configuration.WebConfigurationManager.AppSettings
let hostSiteSettings = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("/Default Web Site") |> Option.ofObj |> Option.map (fun config -> config.AppSettings.Settings)

let allSettings = 
    seq { 
        match hostSiteSettings with
        | None -> ()
        | Some settings -> 
            for key in settings.AllKeys do
                yield (key, settings.[key].Value)

        for key in localSettings.Keys do
            yield (key, localSettings.[key]) 
    } |> Map // using a map here makes it so that if we have any keys in the local config that clobber a key in the appsettings, we overwrite it instead of a duplicatekeyexception from a dictionary add.