Bitcoin-Qt: updates to addressbookpage

- use labelExplanation for sending and receiving tab and move the string
  from the ui-file to the source
- ensure that the table holding the label and address is resized so that
  the address column fits the address and the label column is stretched to
  fit the window size
- rename some stuff for much easier readbility in the code (I find it hard
  to get the meaning of stuff like labels or buttons)

src/qt/forms/addressbookpage.ui

@@ -16,9 +16,6 @@
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <widget class="QLabel" name="labelExplanation">
-     <property name="text">
-      <string>These are your Bitcoin addresses for receiving payments. You may want to give a different one to each sender so you can keep track of who is paying you.</string>
-     </property>
      <property name="textFormat">
       <enum>Qt::PlainText</enum>
      </property>
@@ -58,7 +55,7 @@
    <item>
     <layout class="QHBoxLayout" name="horizontalLayout">
      <item>
-      <widget class="QPushButton" name="newAddressButton">
+      <widget class="QPushButton" name="newAddress">
        <property name="toolTip">
         <string>Create a new address</string>
        </property>
@@ -72,7 +69,7 @@
       </widget>
      </item>
      <item>
-      <widget class="QPushButton" name="copyToClipboard">
+      <widget class="QPushButton" name="copyAddress">
        <property name="toolTip">
         <string>Copy the currently selected address to the system clipboard</string>
        </property>
@@ -125,7 +122,7 @@
       </widget>
      </item>
      <item>
-      <widget class="QPushButton" name="deleteButton">
+      <widget class="QPushButton" name="deleteAddress">
        <property name="toolTip">
         <string>Delete the currently selected address from the list</string>
        </property>