overlay: Update dev-qt/qttools to 5.4.0
overlay: Update dev-util/bless to 0.6.0-r2 & fix mono runtime version

 - Merge changes of dev-util/bless-0.6.0-r2 from Portage tree.

 - Fix failure caused by mono using .NET 2.0 runtime by default, by
   specifying runtime version v4.0.30128 in src/bless-script.in, which
   becomes /usr/bin/bless .