Merge branch 'release-0.4.1'
      o (feature40) flush commentary's content when the reading mode changes.
      o (feature38) 'readingmodeAct' icon is not displayed anymore if no Dipydoc has been loaded : I added the DipylonUI::at_least_one_dipydoc_has_been_loaded() method which should be rewritten when the project accept several dipydocs opened.
      o (feature35) The third reading mode ('read mode') has been defined, allowing to display the translation on the fly, when the mouse hovers over an extract. The UI has been updated and the Dipydoc's format slightly amended (version #30).
      o + feature39, feature37, feature36, feature34, feature33
(UI::UI()) improved debug messages
Merge branch 'feature49' into dev
  (UI::UI()) improved debug messages.
bumped version to 0.4.2
o feature41, feature42 : new splashscreen, new application's icon.
o feature43, feature44, feature45 : the UI has been cleaned up : no more
  useless icons.
o feature46 : Each Dipydoc folder now contains a 'menuname' file : in this
  file, a unique line gives the name of the Dipydoc that appear in the
  submenu 'File>Open'. The UI serches in the default folder all the available
  Dipydoc and add them to this submenu.
o + feature47, feature48, feature49
Merge branch 'release-0.4.2'
o feature41, feature42 : new splashscreen, new application's icon.
o feature43, feature44, feature45 : the UI has been cleaned up : no more
  useless icons.
o feature46 : Each Dipydoc folder now contains a 'menuname' file : in this
  file, a unique line gives the name of the Dipydoc that appear in the
  submenu 'File>Open'. The UI serches in the default folder all the available
  Dipydoc and add them to this submenu.
o + feature47, feature48, feature49
(MainWindow::add_open_menu) added a special display if no Dipydoc could be found
Merge branch 'feature50' into dev
(MainWindow::add_open_menu) added a special display to "File>Open>" if no Dipydoc could be found.