Update documentation mismatches in other getConfigAttribute*().

Clang format run on near-the-header lines.

Happy New Year

Unfortunately the Visual Studio 2015 does not support
the platform independent style for the function attributes.
Although it is a c++11 standard.

This potentially saves a second copy compared to using const
reference. See Effective Modern C++, Item 41.

The access now must be done through some non-member functions.

Also checks are made publicly callable

const + mutable enable use as temporary variables
move assignment complements move construction