Clean up error and info display a little bit

src/libtomahawk/playlist/dynamic/echonest/EchonestControl.cpp

@@ -181,6 +181,7 @@ Tomahawk::EchonestControl::updateWidgets()
 
         QLabel* match = new QLabel( tr( "similar to" ) );
         QLineEdit* input =  new QLineEdit();
+        input->setPlaceholderText( "Enter any combination of song name and artist here..." );
 
         m_matchString = QString();
         m_matchData = QString::number( (int)Echonest::DynamicPlaylist::SongRadioType );

src/libtomahawk/playlist/dynamic/echonest/EchonestGenerator.cpp

@@ -349,7 +349,7 @@ EchonestGenerator::onlyThisArtistType( Echonest::DynamicPlaylist::ArtistTypeEnum
     if( some && only ) {
         return true;
     } else if( some && !only ) {
-        throw std::runtime_error( "All artist match types must be the same" );
+        throw std::runtime_error( "All artist and song match types must be the same" );
     }
 
     return false;