[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/qvalidatedlineedit.h

@@ -15,20 +15,25 @@ class QValidatedLineEdit : public QLineEdit
     Q_OBJECT
 
 public:
-    explicit QValidatedLineEdit(QWidget *parent = 0);
+    explicit QValidatedLineEdit(QWidget *parent);
     void clear();
+    void setCheckValidator(const QValidator *v);
 
 protected:
     void focusInEvent(QFocusEvent *evt);
+    void focusOutEvent(QFocusEvent *evt);
 
 private:
     bool valid;
+    const QValidator *checkValidator;
 
 public slots:
     void setValid(bool valid);
+    void setEnabled(bool enabled);
 
 private slots:
     void markValid();
+    void checkValidity();
 };
 
 #endif // QVALIDATEDLINEEDIT_H