[Qt] extend validate line edit and btc address validator

- remove btc address length from address validator
- add an optional btc address check in validated line edit that defaults
  to off and is used in GUIUtil::setupAddressWidget()
- an isAcceptable() check is added to validated line edit on focus out
  which only kicks in, when a validator is used with that widget
- remove an isAcceptable() check from sendcoinsentry.cpp
- remove obsolete attributes from ui files, which are set by calling
  GUIUtil::setupAddressWidget()
- move some more things to GUIUtil::setupAddressWidget() and remove them
  from normal code e.g. placeholder text

src/qt/guiutil.h

@@ -9,6 +9,7 @@
 #include <QObject>
 #include <QString>
 
+class QValidatedLineEdit;
 class SendCoinsRecipient;
 
 QT_BEGIN_NAMESPACE
@@ -32,7 +33,7 @@ namespace GUIUtil
     QFont bitcoinAddressFont();
 
     // Set up widgets for address and amounts
-    void setupAddressWidget(QLineEdit *widget, QWidget *parent);
+    void setupAddressWidget(QValidatedLineEdit *widget, QWidget *parent);
     void setupAmountWidget(QLineEdit *widget, QWidget *parent);
 
     // Parse "bitcoin:" URI into recipient object, return true on successful parsing