Sage-combinat-widgets

* 2 functions returning buttons: help specifying the main widget
* FlippingDominos example
* Fixed documentation compilation and display

* Show errors on the cells, with tooltips

* Dirty editing
* Signatures changed in the adapters

* ColorTableaux example

* Flexibility options in widget redraw
* Flexibility options: addable cells can be of a different class
* Flexibility in computing distribution of cell classes
* Reverting graphical edit when not valid
* Computing height directly in the widget (for French-style display)
* More tests, esp. for add_links ; couple of bugfixes
* A first example worksheet (Flocon)

* Tutorial completed
* Small fixes, tests