use a sparql request on wikidata to get the list of currencies.
currencies.json contains the translation for all supported searx languages.
Supersede #993
* searx understand "!ddg !g time" as : send "!g time" to DDG
* !g a DDG bang for Google: DDG return a HTTP redirect to Google
This commit adds a the allows_redirect param not to follow HTTP redirect.
The DDG engine returns a empty result as before without HTTP redirect.
the query "time" is convinient because most of the search engine will return some results,
but some engines in the general category will return documentation about the HTML tags <time> or <input type="time">
see searx.search.processors.abstract.EngineProcessor
First the method searx call the get_params method.
If the return value is not None, then the searx call the method search.
