Setup redirects from old i-p.o locations to new ones

[bernhold]

• https://ideas-productivity.org/ideas-classic/ --> https://ideas-productivity.org/activities/ideas-classic/
• https://ideas-productivity.org/ideas-ecp/ --> https://ideas-productivity.org/activities/ideas-ecp/
• https://ideas-productivity.org/ideas-watersheds/ --> https://ideas-productivity.org/activities/ideas-watersheds/
• https://ideas-productivity.org/events --> https://ideas-productivity.org/resources/events.html
• https://ideas-productivity.org/events/hpc-best-practices-webinars/#webinar??? --> https://ideas-productivity.github.io/resources/past-events.html#webinar???

[bernhold]

Added these redirects