[the-board] (10 commits) ...[ui] Update dragArea on ensureDragArea

[Lucas Rocha <lucasr src gnome org>]

Summary of changes:

  5f835c6... [ui] Allow creating toolboxes without a title (*)
  1c78405... [ui] Remove unused enum from Thing (*)
  6eef49d... [ui] Rename _createToolbar() to _createMainToolbar()
  ab199a5... [ui] Emit 'selected-things-changed' when selection changes 
  2711415... [ui] Implement selection context toolbar
  79dfc34... [ui] Rename _LAYER_TOOLBOX to _LAYER_TOOLBAR
  17394b0... [ui] Coding style fix in MainWindow
  e82e7ab... [ui] Unselect all if dragging starts on an unselected thing
  580ce46... [ui] Do not allow selection switches while thing is active
  03efe3e... [ui] Update dragArea on ensureDragArea

(*) This commit already existed in another branch; no separate mail sent