Updated Czech translation
Make the header bar's buttons center align: Closes #729771
Unbind from src properties when widget destroyed: Closes bug #730263

base-properties helper methods didn't deal with lifecycle of generated
Binding object properly, meaning it was impossible to unbind from the
source object when the target object was destroyed, leading to bad
references when properties changed.
Merge branch 'master' into wip/725767-week

Conflicts:
	src/host/host-main-window.vala