* Remove reference to ABI namespace in examples

* Refactor bsoncxx::v_noabi as a non-inline namespace

* Add using-declarations to redeclare entities in root namespace

* Update CONTRIBUTING with root namespace qualifier guidelines

* Replace use of inline namespace macros with v_noabi

* Document top-level and v_noabi namespaces in prelude headers

* Update input paths and files to Doxygen

* Address warnings for undocumented entities

* Remove unused relates documentation for friend declarations

* Address undocumented parameter warnings

* Address ambiguous reference warnings for friend eclarations

* Address warnings for documentation of unnamed parameters

* Use @copydoc instead of group to document parameters

* Add missing generated macros to Doxygen config

* Ensures stdx entities are also documented

* Exclude detail namespace from Doxygen documentation

The prior approach to selecting headers was to include all headers, then
exclude ones matching a regex pattern.  This was too greedy, matching parent
directories as well.

The new approach renames all private headers to .hh, which are excluded
from the list of headers to install.