New archived-styled page for old conferences

[ceciliasharp]

Create a slimmer archive-style page for former Conferences. Containing:

• all the sessions listed with it's speakers, still linking to the speaker page. easy access to the video link (if any). We can debate about showing video and description directly on the first page or not but I think that the speaker page should remain if someone have linked to it.
• all the sponsors
• link to image library for THAT year (now we always have a link to previous one, that make sence for the current conference but as soon as it gets archived…)
• Any other relevant thing from that year.

[ceciliasharp]

Navigation on that page should be "go back to current conference" and all the other old once. Then we can just have ONE link to this page instead of all the different years. Default should be the last old one.