Add sample data

[lochhh]

The code examples in the current user guide are only applicable to internal users (with access to ceph and the DataJoint (DJ) database). We should consider adding sample datasets, potentially on zenodo, so that external users can try out the code examples. The proposed dataset would be 2h from a social experiment, post-social phase, where scale was working fine.

• Add sample data
• Add instructions to access sample data #26
• Consider setting up a sample DJ-database #32
• Update user guide examples #27