[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/forms/editaddressdialog.ui

@@ -47,7 +47,7 @@
       </widget>
      </item>
      <item row="1" column="1">
-      <widget class="QLineEdit" name="addressEdit">
+      <widget class="QValidatedLineEdit" name="addressEdit">
        <property name="toolTip">
         <string>The address associated with this address list entry. This can only be modified for sending addresses.</string>
        </property>
@@ -67,6 +67,13 @@
    </item>
   </layout>
  </widget>
+ <customwidgets>
+  <customwidget>
+   <class>QValidatedLineEdit</class>
+   <extends>QLineEdit</extends>
+   <header>qvalidatedlineedit.h</header>
+  </customwidget>
+ </customwidgets>
  <resources/>
  <connections>
   <connection>

src/qt/forms/signverifymessagedialog.ui

@@ -47,9 +47,6 @@
            <property name="toolTip">
             <string>The address to sign the message with (e.g. 1NS17iag9jJgTHD1VXjvLCEnZuQ3rJDE9L)</string>
            </property>
-           <property name="maxLength">
-            <number>34</number>
-           </property>
           </widget>
          </item>
          <item>
@@ -260,9 +257,6 @@
            <property name="toolTip">
             <string>The address the message was signed with (e.g. 1NS17iag9jJgTHD1VXjvLCEnZuQ3rJDE9L)</string>
            </property>
-           <property name="maxLength">
-            <number>34</number>
-           </property>
           </widget>
          </item>
          <item>