Fix for issue #6 and partial fix of issue #18: Now correctly honour the optionActive flag to draw the pane title, and never automatically set the active window when wxAUI_MGR_ALLOW_ACTIVE_PANE is not set.
This is a better fix for issue #6: active pane management
We now assume that we always track the active pane through the optionActive flag, and we just use the wxAUI_ALLOW_ACTIVE_PANE to draw (or not) the feedback of pane activation. This is conformant to the behaviour described in the documentation of the original wxAui.

This also fixes issue #21: field m_icon is now copied in wxAuiPaneInfo.
We should not clear the activation flag when doing an Update() in the wxAui manager
Icon management cleanup that address the following:
- removed duplicate bitmap field (m_icon and m_dock_bitmap); we keep only m_dock_bitmap
- removed the GetIcon() / SetIcon() interface to keep only GetBitmap() / SetBitmap(); this is more consistent with other wxWidgets API
- addition of the missing legacy wxAuiPaneInfo::icon. It is now aliased to m_dock_bitmap and marked as deprecated.
We can now dig a bit more in icon drawing issues
Reordered wxAuiInfo field initializations in constructors to avoid the GCC red-order warnings
Fix issue #14: incorrect rendering of icons in notebooks
Code cleanup: useless inits removed in local variables
Fix for issue #25: creating notebooks by program is a bit tedious, so introduced a new method to do it easily: wxAuiPaneInfo::MoveOver()
The page number in wxAuiPaneInfo was not honoured when the notebooks were not created manually. A side effect of this is having weird jumps when dragging pages because this relies on having page number consistent with the tab order. This fix both problems.
Merge pull request #28 from lpoujoulat/wxAuiExperimentalFixes

Fix for issue #6 and partial fix of issue #18: active pane management