Refactor qbclient configuration for a better DX

[cpliakas]

This is gross:

func NewQuickbaseClient(cfg *qbclient.ConfigFileProfile) *qbclient.Client {
	v := viper.New()
	v.SetDefault(qbclient.OptionRealmHostname, cfg.RealmHostname)
	v.SetDefault(qbclient.OptionUserToken, cfg.UserToken)
	v.SetDefault(qbclient.OptionTemporaryToken, cfg.TemporaryToken)
	return qbclient.New(qbclient.NewConfig(v))
}

We can do better.

[cpliakas]

Maybe https://github.com/mitchellh/mapstructure will help.