Enable grid by default in Designer's form layout editor

Enable grid by default in Designer's form layout editor

• add the default gap - 16px
• add missing properties for grid cells (children) - harcode
  COLUMN: 'data-column',
  COLUMNSPAN: 'data-column-span',
  ROW: 'data-row',
  ROWSPAN: 'data-row-span',
  ALIGN: 'data-align',
  JUSTIFY: 'data-justify'

AC

• When no widget is selected, I can access the grid properties by using the properties tab, in
  • Document type layouts (create, edit etc)
  • Layout blocks
  • Workflow tasks layouts
  • Search form layouts
• Properties are available to configure
  • Number of rows
  • Number of columns
  • Gap between cells: default value is 16px

• When changing the grid properties
  • a grid element is added inside the layout with these values
  • values reflect on the visual editor
• When reverting to the default values for the grid properties (i.e. no grid), grid element is removed from the code

• When a widget is selected, I access the widget's properties when using the properties tab
  • Children properties described above are available for a widget if a grid is used
  • They are not available visually if no grid is added to the layout
  • Their value is kept when the grid is removed

• When I drag and drop an element into a cell, the element is added into it
• When an element is already present in a cell
  • drag and dropping something into that cell does not replace that element
  • it adds the element into a new cell inserted at the position where you drop it

• When I drag and drop an element in a non-existing area, it is added to the bottom of the grid in a new cell