[GroupBundNaturschutzBridge] Add bridge and adjust XPathAbstract

[dweipert-3138720606]

This adds a bridge for the subdomains of https://bund-naturschutz.de.
The local groups with corresponding subdomains are listed here: https://www.bund-naturschutz.de/ueber-uns/organisation/kreisgruppen-ortsgruppen

I named the bridge GroupBundNaturschutzBridge because it doesn't actually get the news from bund-naturschutz.de, but from its groups. Where each group has its own subdomain.

All groups are working, except for the ones I commented out, mainly because they didn't use the subdomain pages and therefore had a different HTML layout.

I'm not sure about the exact name, description and parameter name regarding what should be written in english or german.
I guess the parameter name could be Kreisgruppe? Or should it stay Group?

@Niehztog I had to adjust the XPathAbstract.php in the process of creating this bridge.

Some images were named $image.JPG, so I added the case-insensitive modifier to the regex.
Other images had % encoded paths and didn't match the regex correctly, that's why I added the \% there as well.

I'm capturing a DOMText node with the XPath text() function, so I had to adjust the check when getting the value to include DOMText objects.

[Niehztog]

@DRogueRonin Your changes to XPathAbstract.php look meaningful. In my opinion it would make sense to merge them.
Regarding your additions around DOMText: I already have an open pull request adressing this issue: #2324
Maybe we can merge our changes together.

[dweipert-3138720606]

You could add my XPathAbstract.php changes to your PR and I could remove them from mine?

[Niehztog]

I have merged your changes to XPathAbstract.php into my pull request. I am not sure though if and when it will be merged. Lets just wait and see what @em92 says about this.

[dweipert-3138720606]

I fixed the code according to the failed phpunit tests, I forgot to check that locally.

[dvikan]

@DRogueRonin This PR still good?

[Bockiii]

bridge

[Bockiii]

I'm not the biggest fan of xpathabstract bridges (as its often just "here be prefilled values") but in this case I think it's valuable. Expanding the posts would be even cooler, but I think that would add a lot of complexity (and tbh, I dont think this bridge will have many users).

So thanks, will merge.