[deviantart] support '?catpath=/' URLs (#26)

They previously weren't supported for galleries and journals.

This also increases the 'limit' parameter for API calls to its
respective maximum.

gallery_dl/extractor/4plebs.py

@@ -14,9 +14,8 @@ from . import chan
 class FourplebsThreadExtractor(chan.FoolfuukaThreadExtractor):
     """Extractor for images from threads on 4plebs.org"""
     category = "4plebs"
+    root = "https://archive.4plebs.org"
     pattern = [r"(?:https?://)?(?:archive\.)?4plebs\.org/([^/]+)/thread/(\d+)"]
     test = [("https://archive.4plebs.org/tg/thread/54059290", {
         "url": "fd823f17b5001442b941fddcd9ec91bafedfbc79",
-        "keyword": "97f66d93f6c87b9dc33314a5f9dc7add6ce067e7",
     })]
-    root = "https://archive.4plebs.org"