ensure clean and consistent "namespace" usage

- remove some missplaced ;
- ensure end of a namespace is clearly visible
- use same formatting when using namespace
update coding.md to reflect changes by pull

- also mention alphabetical include ordering
Merge pull request #4398

86fe1b8 update coding.md to reflect changes by pull (Philip Kaufmann)
e10dcf2 ensure clean and consistent "namespace" usage (Philip Kaufmann)