Improvements for Kanban feature

[nuttyartist]

Tacking here all related issues for the new Kanban view. When tackling a particular issue we can open a separate issue for it.

Code Improvements::

• Replace setContextPropery with qmlRegisterSingletonType
  https://raymii.org/s/articles/Qt_QML_Integrate_Cpp_with_QML_and_why_ContextProperties_are_bad.html#toc_4
• How to pass to delegates other objects aliases without getting Unqualified Access warning by qmllint? (Should make QML better compile to C++)
• Copy the behavior of react-beautiful-dnd - we need to have two Drag.hotSpots. One at the top, one at the bottom. This will allow for an improved dragging experience (especially for long tasks).

Known issues:

• Rearranging columns don't work from a certain height.

Future features (I'll open a new issue for this later):

• Support sub tasks with collapsable feature. Rounded progress-bar for tasks with sub tasks.
• Add option to add labels to tasks. Therefore we'll need another view that shows 1. All tasks under a labdel (list) or multiple labels (kanba/board). Therefore we can have separation between tasks lifecycle and tasks' topic. See below example.
• Support Ctrl y/z in kanban. We can implement a hacky way by remembering how many operations are TextEdit did for a particular action and then ctrl z/y the amount of times necessary and re-render the kanban.
• Keyboard support
• Option to view one task/card - opens the task in a big popup so users can focus on the task at hand. We can elide the text if it's long.
• Button for column creation inside the list view (similar to Trello).
• Tooltips for custom buttons (we'll need to create them from C++ since QQuickView can't render outside its box), but should be easy
• Remembering what view each note is shown (text/kanban) via the database
• Make the kanban optionally on the right/left/bottom/up of TextEdit, so you can edit your text/kanban while seeing both side by side.
• When we implement synchrnoise blocks we could show in the kanban tasks from different notes
• Support RTL
• Emoji picker inside task's text
• Images in tasks

Example for the uses of labels for differentiating tasks' lifecycle and topic/epic/label:
Lifecycle example:

TODO	In Progress	Done	etc...
todo1	todo2	todo3	todo4
#project1, #project2	#project3	#project1	#project3

Topic/epic/label example:

project1	project2	project3
todo1	todo1	todo2
todo3		todo4