Extend MessageHandler for showing multiple messages

[rugk]

Currently MessageHandler can only show one message.

In the future, it could be necessary to show multiple messages, so these have to be created.

What has to be done?

• dynamically clone HTML elements
• maybe get away from IDs in these, as when they are cloned they are not unique anymore, maybe a class may be better

[rugk]

It should maybe best be done by adding custom message types in the JS and thus all other functions can then be used as usual. (maybe they also need some expansions though)

[rugk]

I'd say this is rather low-prio right now, because I have no need for moire message types/custom messages. Currently one is always enough. 😃

[rugk]

BTW with #79, I've changed the message handler a bit and it now also allows to pass in custom HTML elements. It still not really swallow cloning of one message type or so, but my use cases for it are covered by the current behaviour…

[rugk]

I'll do this with what i mentioned here.