refs #575, using livery completer

* embedded in form
* rectified readOnly / only for selection
* added uper case validator where missing
* selecting airline triggers loading of default livery

src/blackgui/components/dbairlineicaoselectorbase.cpp

@@ -125,12 +125,10 @@ namespace BlackGui
                     Q_ASSERT_X(c, Q_FUNC_INFO, "missing converter");
                     this->connect(c, static_cast<void (QCompleter::*)(const QString &)>(&QCompleter::activated), this, &CDbAirlineIcaoSelectorBase::ps_completerActivated);
                     m_completer.reset(c); // deletes any old completer
-                    this->setReadOnly(false);
                 }
                 else
                 {
                     this->m_completer.reset(nullptr);
-                    this->setReadOnly(true);
                 }
             }
         }