[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/sendcoinsentry.cpp

@@ -28,9 +28,7 @@ SendCoinsEntry::SendCoinsEntry(QWidget *parent) :
 #endif
 #if QT_VERSION >= 0x040700
     ui->addAsLabel->setPlaceholderText(tr("Enter a label for this address to add it to your address book"));
-    ui->payTo->setPlaceholderText(tr("Enter a Bitcoin address (e.g. 1NS17iag9jJgTHD1VXjvLCEnZuQ3rJDE9L)"));
 #endif
-    setFocusProxy(ui->payTo);
 
     // normal bitcoin address field
     GUIUtil::setupAddressWidget(ui->payTo, this);
@@ -121,7 +119,7 @@ bool SendCoinsEntry::validate()
     if (recipient.paymentRequest.IsInitialized())
         return retval;
 
-    if (!ui->payTo->hasAcceptableInput() || !model->validateAddress(ui->payTo->text()))
+    if (!model->validateAddress(ui->payTo->text()))
     {
         ui->payTo->setValid(false);
         retval = false;