Replace DRing for libjami

It's not possible to replace the DRing namespace for jami because of conflicts
with namespaces and classes defined under the jami namespace.  Thus, use libjami
as the namespace.

Script to reproduce:

 rg -l DRing | sort | uniq | awk '$0 !~ /NEWS/' | xargs sed -i -e 's|DRing|libjami|g'
 rg -l DRING_ | sort | uniq | xargs sed -i -e 's|DRING_|LIBJAMI_|g'
 sed -i -e 's|dring|jami|g' src/jami/CMakeLists.txt
 sed -i -e 's|dring|jami|g' src/jami/def.h

Change-Id: I80e8c8b58a7586527a016bbef850bab07869c473