Added server update listener

[d.healey]

Tell me more :)

[ustk]

I immediately thought "license", or "update"... But it seems related to the markdown panel only...

[Christoph Hart]

yes, basically it's just a way of displaying on the UI when the docs are being fetched from the server. Otherwise people will see an empty page for 5 seconds and think it's broken.

I don't think it's hooked up to the HISE floating tile yet (somebody's using it in his C++ project...)