Updated POT-file, added Spanish and Polish, fixed bug with Ctrl+U,O,L in Italian

resources/localization/it/Slic3rPE_it.po

@@ -214,7 +214,7 @@ msgstr "&Carica Gruppo di Configurazioni…"
 
 #: c:\src\Slic3r\lib\Slic3r\GUI\MainFrame.pm:254
 msgid "&Load Config…\tCtrl+L"
-msgstr "Carica Configurazione…\tCtrl+&L"
+msgstr "&Carica Configurazione…\tCtrl+L"
 
 #: c:\src\Slic3r\xs\src\slic3r\GUI\GUI.cpp:339
 msgid "&Localization"
@@ -1856,7 +1856,7 @@ msgstr "Aprire un modello"
 
 #: c:\src\Slic3r\lib\Slic3r\GUI\MainFrame.pm:251
 msgid "Open STL/OBJ/AMF…\tCtrl+O"
-msgstr "Aprire un STL/OBJ/AMF… Ctrl+O"
+msgstr "Aprire un STL/OBJ/AMF… \tCtrl+O"
 
 #: c:\src\Slic3r\lib\Slic3r\GUI\Plater.pm:2102
 msgid "Open the 3D cutting tool"
@@ -2003,7 +2003,7 @@ msgstr "Preferenze"
 
 #: c:\src\Slic3r\lib\Slic3r\GUI\MainFrame.pm:299
 msgid "Preferences…\tCtrl+,"
-msgstr "Preferenze…Ctrl+,"
+msgstr "Preferenze…\tCtrl+,"
 
 #: C:\src\Slic3r\xs\src\libslic3r\PrintConfig.cpp:1171
 msgid "Preferred direction of the seam"
@@ -2079,7 +2079,7 @@ msgstr "Versioni Prusa Edition"
 
 #: c:\src\Slic3r\lib\Slic3r\GUI\MainFrame.pm:268
 msgid "Q&uick Slice…\tCtrl+U"
-msgstr "Slice Rapido… \tCtrl+&U"
+msgstr "Slice &Rapido… \tCtrl+U"
 
 #: c:\src\Slic3r\xs\src\slic3r\GUI\Tab.cpp:335
 msgid "Quality (slower slicing)"

xs/src/slic3r/GUI/Tab.cpp

@@ -2125,7 +2125,7 @@ void Tab::save_preset(std::string name /*= ""*/)
 			return;
 		}
 		if (existing && (existing->is_external)) {
-			show_error(this, _(L("Cannot overwrite an external.")));
+			show_error(this, _(L("Cannot overwrite an external profile.")));
 			return;
 		}
 	}