Merge pull request #32 from lpoujoulat/wxAuiExperimentalFixes

Allow a pane to always dock in a notebook
Fix impossibility to click on expander in dataviewctrl if the expander column is not the first one
Fix for toggable fields in wxDataView with variable lines height
Fix issue #16133: wxRibbonBar::ShowPanels() problem
Revert "Fix issue #16133: wxRibbonBar::ShowPanels() problem"

This reverts commit 972df7d66c5413d9e0853202f6ebb3e272ed9500.
Fix for inconsistency of wxRibbonBar display
Allow dropping on the wxDataViewCtrl background area
Allow docking in the centre/background wxAui area