General - improve filter

[MFlisar]

Currently you have to define groups and can filter them in the notification logger. This logger should be replaced with the overlay logger and I want to add another grouping feature for it without the need of custom classes (they were only for type safety and for extensibility, but I think there is nothing that can be added to a group than a name).

So what I want:

• no need to define groups - user can decide to use dynamic strings or define static string constants and uses them
• the filter function (in the future) should extract all the groups dynamically from the receiver log messages

[MFlisar]

Done in v2...