CppEditor: Insert/move member definition right after enclosing class

When triggering move or insert definition outside and no other class
symbol is found in the file, the definition is moved or inserted right
after the enclosing Class.

Change-Id: I74ffa872015753ba7372e21b868d3cf7fa49e84a
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>