Renamed all wrapper class, and moved all text-related classes to plugins/qt_text.py.

Leo build: 20140831120256
Further clarifications of classes in headlines.  All tests pass.

Leo build: 20140831124337
Alphabetized classes, removed section references.

Leo build: 20140831124924
A grand renaming and reorganization of text and wrapper classes:
- All wrapper classes define self.widget for external use.
- Qt-related classes define self.qt_widget for internal use.
- Replaced bodyCtrl by wrapper everywhere.
- Changed self.w to self.qt_widget in several classes.

Leo build: 20140831205734
Another round of changes:
- backed out of the ill-conceived qt_widget plan.  Now, any widget is always a real qui widget.
- Scintilla widget now appears properly in the body pane if the use_scintilla option is True.
  Much more work is needed before this widget becomes functional.

Leo build: 20140901092808
A major reorg of Qt text class: they now use QTextMixin rather than leoFrame.BaseTextWrapper.
This clarifies the code considerably and in any case was required for QScintilla support.
All tests pass. Still somewhat experimental code.

Leo build: 20140901125824
A massive, important simplification: qt_text.py is now independent of leoFrame.py.
The QTextMixin class now contains most of the Qt-widget-independent code.
This eliminates lots of pointless redirection.  In fact, most of the so-called "base-class" code in leoFrame.py could disappear.

Leo build: 20140901191916
The QHeadlineWrapper class is now  subclass of QLineEditWrapper.
This removes lots of duplicate code.
All tests pass.

Leo build: 20140901195244
Cleaned headline in leoNodes.py.

Leo build: 20140902074309
Cleaned headline in qt_text.py

Leo build: 20140902074506