Feature: blocks-like events

[pdpino]

Add support for block-like events #220, see a png demo in the docs

• This will help with multiple issues (I will check them individually to provide examples, e.g. Is there a way where we can avoid shrinking of the events occuring at the same time and ovelap it instead? #235, Add business hours #140, Is it possible to change the background color of specific time blocks? #92)
• I added the special field "eventKind". I do not like the name "event kind" that much, but I couldn't think of a better option 😅 (e.g. "eventType", but "type" has many meanings)

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Code changes:

• Main code changes are in box.js, where block vs standard events are handled
  • block-like events are shown as one box
  • standard events are "unrolled" into multiple boxes if necessary
• The changes in Events.js are to support boxes that are wider than 1 day

[hoangnm]

Thank @pdpino . LGTM