Add support for a Payment Protocol to Bitcoin-Qt.
Payment messages are protocol-buffer encoded and communicated over
http(s), so this adds a dependency on the Google protocol buffer
library, and requires Qt with OpenSSL support.
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>
- the send coins context menu entry was not working anymore, because
a non current version of #2220 was merged onto current master
- also removes some unneeded spaces and adds a comment to
WalletModel::getNumTransactions()
