Move sample files to samples/ directory

This removes the need for the .sample file extension.
Modify Version.targets to generate a single AssemblyInfo

In the previous version, the item Input_ProjectDirs (defined in the Input.targets file) was used to specify which VS projects would get a generated AssemblyInfo file.

The new design uses a simpler, more elegant approach:
- Generate a single CommonAssemblyInfo.cs that contains all assembly attributes (except AssemblyTitle and AssemblyDescription) that gets linked in by the projects in your solution that want it.
- Those same projects would also have a local AssemblyInfo.cs file that then contained the AssemblyTitle and AssemblyDescription attributes.
Modify Package.targets to allow multiple packages

In the previous version, only a single package could be created and that was driven via the Input_Package* properties in the Input.targets file as well as a .nuspec.template file typically in your build directory.

Package creation in the new design is driven by the existance of a .nuspec.template file in the VS project director(ies) for which to build a package.  The scripts then follow the same approach of running 'nuget pack' with the .csproj but then using a .nuspec file (generated from the .nuspec.template) to feed in additional metadata.
Move *_OutputDirPath prop Build.proj > Input.targets

This makes the output directory configurable by consumers of the project.
Move scripts to scripts/ directory

This is for better packaging of the scripts (since we may be adding more directories in the future, like 'tests').
This is the first commit of two that only involves the file moves.
Update paths in scripts after move to scripts dir
Use prop for test assembly name pattern

The unit test assembly name pattern is no longer hard-coded in UnitTest.targets, but can now be specified via Input_NUnitAssemblyNamePattern from Input.targets.
Also rename RunUnitTest target to RunUnitTests.
Final tweaks to README.md file