Rich - C++17 improvements + clang-format formatting.

( WIP Until !261 (merged) is merged )

Adopt a few c++17 features

• Nested namespaces. So for instance replace

namespace A
{
   namespace B
   { 
       namespace C
       {
       }
   }
}

with

namespace A::B::C
{
}

• Application of clang-format (with a custom style) to the sources to apply a consistent formatting.