* Use advanceWidth to get the with of the original text

Co-authored-by: Nicolas Werner <nicolas.werner@hotmail.de>

* add sendernames to state events

* Center state events and make them less tiny

Rows in the message bubble design are only as wide as the bubbles. This
lead to invisible hover highlight. Now it's consistent.

This makes them less annoying when scrolling or accessing the popup
menu.

See also #860

Might be unnecessary, but docs are unclear on that.

We explicitly set a parent. We can't assign to
ApplicationWindow.transientParent though, only to
Window.transientParent, so we just call setTransientParent in C++.

The actual reuseItems is still blocked on a few upstream bugs.