Proper meta data for filters

[nilmerg]

The Properties trait is not really what I imagined for filter meta data. Meta data, by definition, only consists of additional data that is not significant to how whatever it is related to, works. So it needs to be a separate object/interface. A separate interface is also one of the flaws I'd see of the Properties trait. When handling/defining filter meta data, I'd expect to be able to quickly identify the usages of said meta data. This doesn't work with dynamic anonymous properties.

This introduces the class ipl\Stdlib\Data which is more of a generic container for data. (Similar to the ConfigObject of Icinga Web 2)
Classes ipl\Stdlib\Filter\Chain and ipl\Stdlib\Filter\Condition implement a new interface ipl\Stdlib\Filter\MetaDataProvider.

General usage:

$rule->metaData()->has('columnLabel');
$rule->metaData()->set('columnLabel', 'Host Name');
$rule->metaData()->get('columnLabel');