Update to ToolBar style to fix image persistance issue

I have come across two problems with the current `ToolBar` styling:

A. The tool bar images are currently getting used as a single static instance. Even with the property `x:Shared="False"` moving the `ToolBar` one over another will cause a rendering failure. 

![imageerror](https://cloud.githubusercontent.com/assets/4823601/4371121/aa21cde4-4312-11e4-9104-3f3bd4cc056f.gif)

**Solution:**

In the ToolTip Styles.xaml, include the image source as a `ContentTemplate`

	<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
						xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
						xmlns:cal="http://www.caliburnproject.org">
		<Style x:Key="ToolBarToggleButton" TargetType="{x:Type ToggleButton}" 
			   BasedOn="{StaticResource {x:Static ToolBar.ToggleButtonStyleKey}}">
			<Setter Property="ContentTemplate">
				<Setter.Value>
					<DataTemplate>
						<Image x:Shared="false" Source="{Binding Icon}">
							<Image.Style>
								<Style TargetType="Image">
									<Setter Property="Width" Value="16" />
									<Setter Property="Height" Value="16" />
									<Setter Property="Stretch" Value="Fill" />
									<Style.Triggers>
										<Trigger Property="IsEnabled" Value="False">
											<Setter Property="Opacity" Value="0.5" />
										</Trigger>
									</Style.Triggers>
								</Style>
							</Image.Style>
						</Image>
					</DataTemplate>
				</Setter.Value>
			</Setter>
			<Setter Property="ToolTip" Value="{Binding FullToolTip}" />
			<Setter Property="ToolTipService.IsEnabled" Value="{Binding HasToolTip}" />
			<Setter Property="IsChecked" Value="{Binding IsChecked}" />
			<Setter Property="cal:Action.Target" Value="{Binding}" />
			<Setter Property="cal:Message.Attach" Value="{Binding ActionText}" />
		</Style>

		<Style x:Key="ToolBarButton" TargetType="{x:Type Button}" 
			   BasedOn="{StaticResource {x:Static ToolBar.ButtonStyleKey}}">
			<Setter Property="ContentTemplate">
				<Setter.Value>
					<DataTemplate>
						<Image x:Shared="false" Source="{Binding Icon}">
							<Image.Style>
								<Style TargetType="Image">
									<Setter Property="Width" Value="16" />
									<Setter Property="Height" Value="16" />
									<Setter Property="Stretch" Value="Fill" />
									<Style.Triggers>
										<Trigger Property="IsEnabled" Value="False">
											<Setter Property="Opacity" Value="0.5" />
										</Trigger>
									</Style.Triggers>
								</Style>
							</Image.Style>
						</Image>
					</DataTemplate>
				</Setter.Value>
			</Setter>
			<Setter Property="ToolTip" Value="{Binding FullToolTip}" />
			<Setter Property="ToolTipService.IsEnabled" Value="{Binding HasToolTip}" />
			<Setter Property="cal:Action.Target" Value="{Binding}" />
			<Setter Property="cal:Message.Attach" Value="{Binding ActionText}" />
		</Style>
	</ResourceDictionary>
	
Now we have:

![imageerrorsolved](https://cloud.githubusercontent.com/assets/4823601/4371125/b5975824-4312-11e4-98f9-06df1fe25785.gif)

No other changes required.

B. When the drag operation shown above occurs, this also breaks the `Message.Attach` and `ToolTip` bindings. 

I have not yet got a solution to this one as I have just found it. I will work on this tonight and provide an update in due course.