Added more collection types, and other tweaks

* DirectedGraph

* Tree

* ReadOnlySet

* Various binary trees:

  * BinaryTree

  * BinaryTreeWithParent

* Moved "Common.TestApp.ConcurrentSpeedTest" to "ConcurrentSpeedTest".

Version changed to 0.4.0.0
Split the source into .NET 4.0 and .NET 4.5

This is really dumb, but Visual Studio does not seem to be very good
about allowing .NET 4.0 and .NET 4.5 builds from the same source
directories.
Fixed spurious StateComply.Data namespace

Version changed to 0.4.1
Fixes to Tree

Version changed to 0.4.2
More fixes to tree

Version changed to 0.4.3
Many changes

* Fixes to Tree

* Added SafeJson

* Moved Math to MathExtensions