feature request: disable_notification

[umbm]

It is possible to add the "disable_notification" parameter as a new send command "bot.sendMessageWithoutNotification"?

In API the parameter disable_notification sends a message without alert-sound at recipients client.
It would be very useful for bots, to send standard messages without notification and only important messages like alarms with notification.

[gemini1389]

Recently I also needed such functionality. Just added to the PR #260. You can take changes from it or wait for a pull request (if there are no problems with it).