Set mappings of elastisearch to work with dini kim lrmi profile

In JSON-LD an '@context' is used to define semantics of JSON fields. These
definitions can consist of an array with mixed data types. This is invalid
when tried to be indexed into elasticsearch. As a mapping of the index can be
defined to ignore the '@context' field for indexing such an JSON-LD document
can then be loaded into elasticsearch.

The mapping must be set when initializing the index. This is done in the
start script provided by skohub-pubsub.

See #40.

scripts/elasticsearch-mappings.json

@@ -0,0 +1,15 @@
+{
+   "mappings" : {
+      "_doc" : {
+         "properties" : {
+            "attachment" : {
+               "properties" : {
+                  "@context" : {
+                     "enabled" : false
+                  }
+               }
+            }
+         }
+      }
+   }
+}

scripts/start.sh

@@ -34,8 +34,8 @@ cd $HOME/git/$NAME/scripts
 ###
 # nothing to change from here
 ###
-# ensure elasticsearch index exists
-curl -XPUT $ES_NODE/skohub
+# ensure elasticsearch index exists and initialize proper mappings
+curl -XPUT $ES_NODE/skohub -H 'Content-Type: application/json' -d "@elasticsearch-mappings.json"
 
 npm install
 # start skohub-pubsub