Added support for a Pie Chart Data Source based on a dictionary.

Made it really easy to create a pie chart from a dictionary of entries, and added ability to add a key chart view of the pie chart based on the dictionary.

The following is an example of setting up a pie chart based on a dictionary.

    _roundsWonLostPieChartView.colorDict      = @{@"Rounds Won": UIColor.redColor,                                         @"Rounds Lost" : UIColor.blackColor };
    _roundsWonLostPieChartView.dataSourceDict = @{@"Rounds Won": @(m_playerStats.roundsPlayed - m_playerStats.lostRounds), @"Rounds Lost" : @(m_playerStats.lostRounds)};
    
    _wonPointsInRoundPieChartView.colorDict      = @{@"Won 1 Point": UIColor.redColor,              @"Won 2 Points" : UIColor.blackColor,            @"Won 4 Points" : UIColor.blueColor };
    _wonPointsInRoundPieChartView.dataSourceDict = @{@"Won 1 Point": @(m_playerStats.wonRounds1pt), @"Won 2 Points" : @(m_playerStats.wonRounds2pt), @"Won 4 Points" : @(m_playerStats.wonRounds4pt) };
    _wonPointsInRoundPieChartView.keyOrder       = @[@"Won 1 Point", @"Won 2 Points", @"Won 4 Points"];

The following is an example of dynamically creating a key legend based on the dictionary and adding it to the right of the pie chart.

        CGPoint point   = CGPointMake( xyPieChartView.frame.origin.x + xyPieChartView.frame.size.width, xyPieChartView.layer.position.y );
        UIView *keyView = [xyPieChartView makeLabelKeyViewAtPoint:point boxCornerRadius:2.0];
        CGRect  frame   = keyView.frame;
        frame.origin.y -= frame.size.height/2;
        keyView.frame = frame;
        
        [_scrollContentsView addSubview:keyView];