[WPF] Don't set the Width/Height properties of widgets

When Width/Height is set, the DesiredSize of the widget returns
the specified size. Instead of setting those properties we now
set RenderSize, which doesn't have any effect on desired size
calculation.
[WPF] Avoid viewport recalculation when the visible are doesn't change
[WPF] Fix size calculation issue with Expander

The OnPreferredSizeChanged method can't be called in the handler of the
Expanded event, since at that point the expander may not yet have the
new size.
[Widget] New virtual method called when the size of a child changes
[WPF] Use the same native widget for Canvas and Box

Code reuse +1
No more <SubType>Component</SubType> in VS
Fixed some bitmap conversion issues

Don't allow specifying an arbitrary width/height ratio when converting
a vector image to a bitmap. Now a scale factor has to be provided.
[GTK] Fix bitmap conversion issue
Track api changes
Make sure children of a widget are always correctly reallocated

The reallocation of the children of a widget is not done anymore in the
default implementation of the OnReallocate virtual method, it is now done
after invoking that method. This ensures that Reallocate is called on the
children after they got their new positions. This avoids common mistakes
when placing widgets in a Canvas, where base.OnReallocate was sometimes
not called or called in the wrong order.
Add Ellipsize support to TextCellView
Use a better name for SortIndicatorVisible property
Better name for IsResizeable property
Update CellUtil.cs

Display Checkboxes in WPF ListView
Minor cleanup

Fix GTK warning assigning null value to entry
Fix disposal of placeholder layout
Clean up some source analysis warnings
Add PasswordEntry.{PlaceholderText,SecurePassword}
Fix bad cast in Gtk PasswordEntryBackend
Merge pull request #241 from steffenWi/master

[Wpf] Update CellUtil.cs to support CheckBox in ListView
Don't use spaces for indenting