Added Toolbar global plugin
Updates to the core display and bindings classes

- improvements to interactive rotation command--now resume rotation from
  current value and direction is relative to horizontal motion of mouse
- most keyboard modes are now locking and not oneshot (press to turn on,
  press again (or hit escape) to turn off
- additional mouse button functionality in modes (see quick reference)
- some changes to default keyboard bindings (see quick reference)
- changes to auto cuts parameters always result in a new autocut being
  done (instead of having to explicity perform the autocut)--users seem
  to expect this
- autocenter preference changed from True/False to on/override/off

Reference viewer only: new global plugin "Toolbar" provides GUI buttons
for many operations that previously had only keyboard bindings
Turn off an active mode for certain plugins

for plugins that utilize conflicting mouse bindings
Fix to align behavior for mode cancellation with other plugins
Bug fix for Info plugin

- fixes reporting for "center new" setting when migrating old preferences
A few bug fixes for Toolbar plugin

- fixes a bug where the toolbar was not updated properly when the focus
    changes to a different view object
- bumped release
Added debugging to file loading code
Fix for bug in ginga.qtw.ipg (ipython notebook use) with PySide
Added recognition of mime-type image/x-fits

- bumped release
Misc bug fixes

- bug fix for Contents plugin (qt) where bad UT value could botch formatting
- fix for import of Matplotlib FigureCanvas (qt)
- fix for python 3
- bumped release
Fix for import error with matplotlib Qt4Agg backend
Workaround for bug in Qt drawing ellipses with radius 0
Add support for alpha in most plotted objects
Updates to graphics

- all backends now support transparency for graphics forms
- triangles can now be filled and rotate with the canvas
- preliminary support for editing object nodes
First cut at generalized canvas
Optomized addition of standard image to canvas
Optimizations to image overlay redraws
Fixes for various examples to accomodate recent changes
Updated IPython notebook demo
Fix for breakage of Thumbs plugin due to recent changes