static_array: data member now private, not using {} initializer.
static_array: data member now private, not using {} initializer.

The {} initializer leads to warnings on Visual Studio, hence reverting to a plain for-loop.
Also, the public member should not be used directly (operator overloads available),
hence now private. Renamed to fulfill internal coding style.

viennagrid/viennagrid-dev,viennagrid/viennagrid-dev,viennagrid/viennagrid-dev