Update Activities fields in admin panel

[Raphael Koh]

We need to update the fields under the Activities segment to cover the newly added fields.

For the display of the activities, we want to add the following columns:

• image URI (link -> make a hyperlink)
• isNewActivity (boolean)
• isOpen (boolean)
• state (description of current state)

For adding a new activity:

• grade (allow selecting multiple grades)
• image URI (link -> make a hyperlink)
• isNewActivity (boolean)
• isOpen (boolean)
• state (description of current state)

[Raphael Koh]

Duplicated in #105