add flexbox editor component

[hebus]

• new flexbox editor component
• flexbox's configuration synchronization delegated to configurator component
• fix typo on "Tree" component filename

Structure description used in the template

  justify = [
    {key:'align_x_start', text: 'start', style: 'flex-start', bootstrap: 'justify-content-start'},
    {key:'align_x_center', text: 'center', style: 'center', bootstrap: 'justify-content-center'},
    {key:'align_x_end', text: 'end', style: 'flex-end', bootstrap: 'justify-content-end'},
    {key:'align_x_space_around', text: 'space around', style: 'space-around', bootstrap: 'justify-content-around'},
    {key:'align_x_space_between', text: 'space between', style: 'space-between', bootstrap: 'justify-content-between'}
  ]

attribute	description
key	svg id used by the svg-icon to display the correct svg
text	tooltip text
style	css if we want use it in style attribute
bootstrap	bootstrap class