Remove explicit default destructors (#157)

From CppCoreGuidelines:

Rule of Zero: C.20: If you can avoid defining default operations, do.
C.52: Use inheriting constructors to import constructors into a derived class that does not need further explicit initialization.
DRY forward and using declarations.
Miscellaneous:

Fix format.sh to output examples with normalised paths in sorted order.

Co-authored-by: ArthurSonzogni <sonzogniarthur@gmail.com>

tools/format.sh

@@ -20,7 +20,7 @@ done
 
 exampleList="./doc/example_list.md"
 echo "# Examples" > $exampleList
-files=$(find ./examples/ -iname "*.cpp")
+files=$(find ./examples -iname "*.cpp" | sort)
 for f in $files
 do
   echo "@example $f" >> $exampleList