the svn command has to be in your path. the implementation of the file explorer was a hasty bit of hacking on my part and still needs lots of enhancements. as you say, I haven't tried to implement the windows explorer shell menu as that will require windows specific code, which is a low priority for me (not to say I won't ever do it)
EDIT: I should ask - what are you trying to do that you need full windows explorer functionality within codeblocks? Personally, I find the inability to control the context menu of windows explorer a frustration, which is why I designed the plugin the way I did.