CppEditor: New quick fix "Optimize For Loop"

Rewrites post increment/decrement operators (++ and --) as pre
increment/decrement operators and moves non string/numeric literals and
non id expressions from loops condition to loops initializer.

Change-Id: Id95334b6df6fcaa9af436cc1d2d0982d38bf8fe2
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>