Rewrite the build scripts using PowerShell

I created an alternative to **MasterBuild.bat** and **BuildReflectionData.bat** which use PowerShell instead of batch files.

These files are nearly the same as the current build script, with the following exceptions.

* Added a `-BuildReflectionData` switch to **MasterBuild.ps1**. When specified, **BuildReflectionData.ps1** will be used to build the reference reflection data. The reflection data is also built if you run **MasterBuild.ps1** when the data is missing.
* Added a `-NoClean` switch to **MasterBuild.ps1**. When specified, the build targets for each solution will be `Build` instead of `Clean;Build`.
* The `-Debug` switch is equivalent to specifying `MasterBuild.bat Debug` with the current build script.
* The `-FrameworkPlatform` and `-FrameworkVersion` string parameters are passed on to **BuildReflectionData.ps1** when the reflection data is being built.
* Specify `/m` when building **AllDocumentation.sln**.

See also: [work item 35043](https://shfb.codeplex.com/workitem/35043)