Reimplement click-to-pay links. Add OSX support.

Switch to using Qt's QLocalServer/QLocalSocket to handle bitcoin
payment links (bitcoin:... URIs)

Reason for switch: the boost::interprocess mechanism seemed flaky,
and doesn't mesh as well with "The Qt Way"

qtipcserver.cpp/h is replaced by paymentserver.cpp/h

Click-to-pay now also works on OSX, with a custom Info.plist
that registers Bitcoin-Qt as a handler for bitcoin: URLs and
an event listener on the main QApplication that handles
QFileOpenEvents (Qt translates 'url clicked' AppleEvents into
QFileOpenEvents automagically).

share/qt/Info.plist

@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist SYSTEM "file://localhost/System/Library/DTDs/PropertyList.dtd">
+<plist version="0.9">
+<dict>
+	<key>CFBundleIconFile</key>
+	<string>bitcoin.icns</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>CFBundleGetInfoString</key>
+	<string>Bitcoin-Qt</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleExecutable</key>
+	<string>Bitcoin-Qt</string>
+	<key>CFBundleIdentifier</key>
+	<string>org.bitcoinfoundation.Bitcoin-Qt</string>
+        <key>CFBundleURLTypes</key>
+        <array>
+          <dict>
+            <key>CFBundleTypeRole</key>
+            <string>Editor</string>
+            <key>CFBundleURLName</key>
+            <string>org.bitcoinfoundation.BitcoinPayment</string>
+            <key>CFBundleURLSchemes</key>
+            <array>
+              <string>bitcoin</string>
+            </array>
+          </dict>
+        </array>
+</dict>
+</plist>