Branch new-chat-logs

[cemunoz]

This branch gives logs functionalities to the chat plugin. It's created from the new-chat-fixes-1, so probably you could just merge this one directly, as it includes all the fixes from the other branch.

Take into account that this branch needs the file code.py, which is not in this repo. Pedro suggested to create a new project for it, since it will probably get bigger, but I guess we can discuss it anyway.

This branch features:

• Possibility of watching the logs for an event, but also of attaching them as material.

• When attaching them as material you are redirected to the material page and the resource gets highlighted.

• Added some docs for the Indico guide.

• Added custom links, but they still need some improvements in terms of design.

• Some bug fixing from the other branch.