etc: several improvements and smaller additions

This release consists of several smaller improvements and additions.
The biggest new feature is the possibility to set configuration values via command line flags with the new application option WithConfigFlags:

application.New(application.WithConfigFlags(os.Args, &struct {
	ServerPort int `short:"p" long:"server-port" cfg:"httpserver.default.port" default:"8080" description:"port of the default http server"`
}{}))

Providing this option would enable to set / overwrite the config value httpserver.default.port with providing -p 8888 or --server-port 8888 as command line arguments.

What's Changed

• justdev changes by @j4k4 in #1199

Full Changelog: v0.36.0...v0.36.1