[mod] Dailymotion: improved request API & upgrade to data_type: traits_v1

- fetch_traits(): fetch locales (and languages) from dailymotion API
- removed obsolete data-type "supported_languages"
- add documentation
- improved argument list of the HTTP request:
  - add argument: family_filter_map
  - add conditional argument: localization
    Don't add localization and country arguments if the user does select a
    language (:de, :en, ..)
- improve code quality (mainly improve readability)

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

searx/data/engine_traits.json

@@ -366,8 +366,29 @@
   "dailymotion": {
     "all_locale": null,
     "custom": {},
-    "data_type": "supported_languages",
-    "languages": {},
+    "data_type": "traits_v1",
+    "languages": {
+      "ar": "ar",
+      "de": "de",
+      "el": "el",
+      "en": "en",
+      "es": "es",
+      "fr": "fr",
+      "id": "id",
+      "it": "it",
+      "ja": "ja",
+      "ko": "ko",
+      "ms": "ms",
+      "nl": "nl",
+      "pl": "pl",
+      "pt": "pt",
+      "ro": "ro",
+      "ru": "ru",
+      "th": "th",
+      "tr": "tr",
+      "vi": "vi",
+      "zh": "zh"
+    },
     "regions": {
       "ar-AE": "ar_AE",
       "ar-EG": "ar_EG",
@@ -418,58 +439,7 @@
       "zh-CN": "zh_CN",
       "zh-TW": "zh_TW"
     },
-    "supported_languages": [
-      "ar_AA",
-      "ar_AE",
-      "ar_EG",
-      "ar_SA",
-      "de_AT",
-      "de_CH",
-      "de_DE",
-      "el_GR",
-      "en_AU",
-      "en_CA",
-      "en_EN",
-      "en_GB",
-      "en_HK",
-      "en_IE",
-      "en_IN",
-      "en_NG",
-      "en_PH",
-      "en_PK",
-      "en_SG",
-      "en_US",
-      "en_ZA",
-      "es_AR",
-      "es_ES",
-      "es_MX",
-      "fr_BE",
-      "fr_CA",
-      "fr_CH",
-      "fr_CI",
-      "fr_FR",
-      "fr_MA",
-      "fr_SN",
-      "fr_TN",
-      "id_ID",
-      "it_CH",
-      "it_IT",
-      "ja_JP",
-      "ko_KR",
-      "ms_MY",
-      "nl_BE",
-      "nl_NL",
-      "pl_PL",
-      "pt_BR",
-      "pt_PT",
-      "ro_RO",
-      "ru_RU",
-      "th_TH",
-      "tr_TR",
-      "vi_VN",
-      "zh_CN",
-      "zh_TW"
-    ]
+    "supported_languages": {}
   },
   "duckduckgo": {
     "all_locale": "wt-wt",