filament guide modified

Lovely original thing. But my printer is quite short on free space in this area : I have already added a fan "door" modification.

Plus I wanted to add an Y chain, thus I had requirements that were not satisfied with original thing :
- make sure the filament would not hit the chain, thus move upper the filament guide
- make the guide "easily unmountable", just in case ... (cold pull that I stil can not achieve, even when puting force like a troll) (or just stuck filament in the hothead)
- a