common.hpp: fix documentation of functions

Functions inside namespace are tough to document, bypassing this by documenting
the namespace and then using the namespace doc as common.hpp doc in the index

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
docs: add references to galileo generation

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>