Default values should be filtered by product

[TorsteinHonsi]

Products are given in curly brackets:

@default {highcharts} true

Multiple products should be supported:

@default {highcharts|highstock} true

When left out, the default should apply to all products:

@default true

Multiple tags should be supported on each doclet:

@default {highcharts|highstock} true
@default {highmaps} false

[cvasseng]

Fixed in plugin (highcharts/highcharts@b8c706c) + in 1e4fb62