Fix issue #183 : New file option - clear document before load (on by default)
Document is never cleared before loading DLL and AX files (instantiating filter from DLL class factory)
If off user can perform operations like creating renderer then opening media file to render it using the existing renderer


git-svn-id: http://graph-studio-next.googlecode.com/svn/trunk@425 c2f33eb2-41b2-391d-4cb4-d9d0608729ba