Modify constructor to accept CompositionContainer

Modified UI components to accept CompositionContainer as part of their constructors.
Allows 3rd party libraries to use them.
Specify assembly name in Pack resource URI for external assemblies
When pressing F3 to move focus to the search box, select the text so that the previous search can be easily overwritten.
Add "Search MSDN..." context menu command.

Contributed by Shawn Shaddock.
Merge remote-tracking branch 'upstream/master'
Allow current Application instance to be specified.
Specify assembly name for pack URI.
Default all text nodes to expanded.
Current synchronization context cannot be used with LINQPad.
Disable ToolTips for now in LINQPad.