update to bitcoinqt.pro (qt4<--->qt5)

This commit squashes all the changes in the Qt5 branch
relative to master.

Backward compatibility with Qt4 is retained.

Original authors:

- Philip Kaufmann <phil.kaufmann@t-online.de>
- Jonas Schnelli <jonas.schnelli@include7.ch>

changes implemented from:
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
create readme-qt.rst

please add a "doc" folder and move this file into that folder
update addressbookpage.cpp

updates implemented from:
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update bitcoin.cpp

changes for qt5 compatibility 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update bitcoingui.cpp

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update guiutil.cpp

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update macdockiconhandler.mm

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update paymentserver.cpp

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update qrcodedialog.cpp

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update rpcconsole.cpp

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update sendcoinsdialog.cpp

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update splashscreen.cpp

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update transactionview.cpp

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update walletframe.cpp

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update walletframe.h

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update walletstack.h

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
update walletview.cpp

changes for qt5 compatibility
source: 
https://github.com/bitcoin/bitcoin/commit/25c0cce7f
Merge pull request #12 from layer1gfx/master

Qt5 compatibility