Recognize .NET 4.5 when it is running

[Charlie Poole]

.NET 4.5 uses the 4.0 CLR and so reports that the 4.0 framework is running in several places.

In the similar case of .NET 3.0 and 3.5 we have code to recognize the actual installed framework. We need to add similar code to RuntimeFramework to distinguish the 4.0 and 4.5 frameworks.

We also need to change labels that display 4.0 to 4.5 where appropriate. This should be done anyplace where we now display the 3.5 framework, for example, in the test assembly listing of the Gui. Places where we are deliberately displaying the CLR version should not change.

Additionally, PlatformAttribute should recognize .NET 4.5. When .NET 4.5 is specified, the test should only run if 4.5 is available. Tests marked with 4.0 should run under both 4.0 and 4.5, as we now do for .NET 2.0, 3.0 and 3.5.