Added support to QPickerElement for submit values

[michelevirgilio]

Now it is possible to use submit values:

NSArray *component1 = @[@"Vendita", @"Affitto", @"Vacanza"];
NSArray *componentValues1 = @[@"V", @"A", @"S"];
NSArray *component2 = @[@"A", @"B"];
NSArray *componentValues2 = @[@"aaaa", @"bbbbb"];
QPickerElement *simplePickerEl = [[QPickerElement alloc] initWithTitle:@"Key"
                                                                 items:@[component1, component2]
                                                           itemsValues:@[componentValues1, componentValues2]
                                                                 value:@"Vacanza\tB"];

Submit value is obtainable by calling

simplePickerEl.submitValue