qt: Move initialization/shutdown to a thread

Move AppInit2 and Shutdown to a thread.

This allows a more responsive splash screen, prevents 'process does not respond'
messages from the window system and will allow for showing a user friendly
window while shutting down.

Author: laanwj

src/qt/Makefile.am

@@ -108,7 +108,7 @@ QT_MOC_CPP = moc_aboutdialog.cpp moc_addressbookpage.cpp \
 
 BITCOIN_MM = macdockiconhandler.mm macnotificationhandler.mm
 
-QT_MOC = intro.moc overviewpage.moc rpcconsole.moc
+QT_MOC = intro.moc overviewpage.moc rpcconsole.moc bitcoin.moc
 
 QT_QRC_CPP = qrc_bitcoin.cpp
 QT_QRC = bitcoin.qrc