Improve basic and advanced search logic

Closes #17, #18 , #19

app/dal/elasticService.js

@@ -80,7 +80,7 @@ async function search({query, sourcesId, advancedQuery}) {
             logger.debug("Advanced query: " + query);
             query = JSON.parse(query);
             queryBuilder = {
-                size: MAXIMUM_HITS_SIZE,
+                size: process.env.MAXIMUM_HITS_SIZE || 10000,
                 query: query
             };
         } catch (error) {