Add a Manage Labor to the event page

[BrianRamsay]

• On Edit event, in manage volunteers, we are going to implement two more columns: "labor" and "volunteer service" checkboxes which are mutually exclusive. There should be a count of hours for either one of the checkboxes checked or for just participation with no labor or service hours.
• "Add volunteers" button should be renamed to "add participants"
• Add an X for deleting participants in the modal when you added one and want to remove it in the modal.
• When we calculate RSVP and waitlist, they should not be added as labor
• Add to "eventparticipant" model new columns in database: isLabor, isService
• When we calculate RSVP and waitlist, they should not be added as labor

[BrianRamsay]

Add Manage Labor tab for events

[Karina-Agliullova]

https://trello.com/c/KCxvcy0z/929-add-manage-labor-tab-for-events