[libcalamares] Use -D for just debug-level setting

- Original flag -d sets debugging but also changes behavior
 - New -D just sets debugging
 - Simplify QStringList (use C++ 11)

src/calamares/main.cpp

@@ -63,11 +63,14 @@ main( int argc, char* argv[] )
     parser.setApplicationDescription( "Distribution-independent installer framework" );
     parser.addHelpOption();
     parser.addVersionOption();
-    QCommandLineOption debugOption( QStringList() << "d" << "debug",
+    QCommandLineOption debugOption( QStringList{ "d", "debug"},
-                                      "Verbose output for debugging purposes." );
+                                    "Also look in current directory for configuration. Implies -D." );
     parser.addOption( debugOption );
 
-    QCommandLineOption configOption( QStringList() << "c" << "config",
+    parser.addOption( QCommandLineOption( QStringLiteral("D"),
+                                          "Verbose output for debugging purposes." ) );
+
+    QCommandLineOption configOption( QStringList{ "c", "config"},
                                      "Configuration directory to use, for testing purposes.", "config" );
     parser.addOption( configOption );
 

src/libcalamares/utils/Logger.cpp

@@ -47,7 +47,8 @@ log( const char* msg, unsigned int debugLevel, bool toDisk = true )
     if ( !s_threshold )
     {
         if ( qApp->arguments().contains( "--debug" ) ||
-             qApp->arguments().contains( "-d" ) )
+             qApp->arguments().contains( "-d" ) ||
+             qApp->arguments().contains( "-D" ) )
             s_threshold = LOGVERBOSE;
         else
 #ifdef QT_NO_DEBUG