Allow sendRedirect() in doBeforeRender() under non-portal environment.

Developers need to redirect page during doBeforeRender() in non-portal environment.
So, developers could choose to invoke HstResponse.sendRedirect() if it's under non-portal environment, or invoke HstResponse.forward() otherwise.
To reduce the burden to check if it's non-portal env or not, we will provide utility methods.
By the way, if a component invokes sendRedirect() in doBeforeRender(), the remaining process on other components will just stop and do forwarding.