Automatically sort member cards by seniority

[kasperjha]

Currently the order members appear on the team page defined manually with the weight attribute in the team collection. This is tedious and requires manual labour. Ideally members could automatically be sorted by their seniority.

• define a good data point to represent seniority (dissertation date?)
• update CMS schema for the team collection
• provide values for new field for entries in team collection
• update the layout of the team page to sort member cards on this new field