Schedule editor improvements v0.5

[marcoacierno]

List of improvements:

• [ ] Create time slots directly
• [ ] Change rooms of an item by "extending" the right/left side of an item
• [ ] Change the duration of an item by "extending" an item from the top/bottom (see a calendar)
• [ ] Show loading states when something is happening
  • [ ] Creating an item
  • [ ] Schedule is refreshing

Nice-to-have / Things to discuss:

• [ ] Websockets updates