[mod] Startpage: reversed engineered & upgrade to data_type: traits_v1

One reason for the often seen CAPTCHA of the Startpage requests are the
incomplete requests SearXNG sends to startpage.com: this patch is a complete new
implementation of the ``request()`` function, reversed engineered from the
Startpage's search form.  The new implementation:

- use traits of data_type: traits_v1 and drop deprecated data_type: supported_languages
- adds time-range support
- adds save-search support
- fix searxng/searxng/issues 1884
- fix searxng/searxng/issues 1081 --> improvements to avoid CAPTCHA

In preparation for more categories (News, Images, Videos ..) from Startpage, the
variable ``startpage_categ`` was set up.  The default value is ``web`` and other
categories from Startpage are not yet implemented.

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/autocomplete.py

@@ -109,9 +109,9 @@ def seznam(query, _lang):
     ]
 
 
-def startpage(query, lang):
-    # startpage autocompleter
-    lui = engines['startpage'].supported_languages.get(lang, 'english')  # vintage / deprecated
+def startpage(query, sxng_locale):
+    """Autocomplete from Startpage. Supports Startpage's languages"""
+    lui = engines['startpage'].traits.get_language(sxng_locale, 'english')
     url = 'https://startpage.com/suggestions?{query}'
     resp = get(url.format(query=urlencode({'q': query, 'segment': 'startpage.udog', 'lui': lui})))
     data = resp.json()