new: [setting] Added new setting to set external baseurl
new: [setting] Added new setting to set external baseurl

- idea is to decouple the baseurl (used to prepend links) from the announce baseurl (for sharing groups / emailing)

SteveClement/MISP,SteveClement/MISP,FloatingGhost/MISP,MISP/MISP,FloatingGhost/MISP,MISP/MISP,FIRSTdotorg/MISP,FIRSTdotorg/MISP,MISP/MISP,SteveClement/MISP,FloatingGhost/MISP,MISP/MISP,MISP/MISP,FIRSTdotorg/MISP,SteveClement/MISP,SteveClement/MISP,FIRSTdotorg/MISP,FloatingGhost/MISP