New column page

Shows SQL for columns ALTER TABLE ... [ADD|DROP] COLUMN combines a selection
of multiple columns into a single alter table.
Show collation in list of columns.

(order of columns isn't what is should be but that should maybe be fixed
by a generic column selection and ordering mechanism that knows what the
default sort should be)

pglab/TablesPage.ui

@@ -38,18 +38,8 @@
      </widget>
      <widget class="QTabWidget" name="twDetails">
       <property name="currentIndex">
-       <number>2</number>
+       <number>0</number>
       </property>
-      <widget class="QWidget" name="columnsTab">
-       <attribute name="title">
-        <string>Columns</string>
-       </attribute>
-       <layout class="QVBoxLayout" name="verticalLayout">
-        <item>
-         <widget class="QTableView" name="columnsTable"/>
-        </item>
-       </layout>
-      </widget>
       <widget class="QWidget" name="tabConstraints">
        <attribute name="title">
         <string>Constraints</string>