Merge IO, NUnit and Microsoft namespaces into core.

The idea is not to keep the seperate namespaces in this core project but
a the moment it will ease development and easier spot design flaws.

Pipes4NET.IO\
Executables working with IO.

Pipes4NET.NUnit\
Executables to be used with NUnit testing framework.

Pipes4NET.Microsoft\
Microsoft specific executables, now only hold capabilities to compile .NET
code with MSBuild.exe.

Assemblies\
Holds the dependencies to the sub namespaces e.g. IO or NUnit.

Also includes some core updates like First, Last and Max.