Added a gutter and currentline highlighting to the SQL editor.

Currently gutter only shows linenumbers. Code is mostly from http://doc.qt.io/qt-5/qtwidgets-widgets-codeeditor-example.html

There is a little bit included in this commit from a first try to make toobars adept to the current tab.

Code #2

pglab/QueryTab.ui

@@ -23,7 +23,7 @@
       <property name="orientation">
        <enum>Qt::Horizontal</enum>
       </property>
-      <widget class="QPlainTextEdit" name="queryEdit"/>
+      <widget class="CodeEditor" name="queryEdit"/>
       <widget class="QFrame" name="frameParams">
        <property name="frameShape">
         <enum>QFrame::StyledPanel</enum>
@@ -213,6 +213,13 @@
    </item>
   </layout>
  </widget>
+ <customwidgets>
+  <customwidget>
+   <class>CodeEditor</class>
+   <extends>QPlainTextEdit</extends>
+   <header>CodeEditor.h</header>
+  </customwidget>
+ </customwidgets>
  <resources/>
  <connections/>
 </ui>