lib: create a new mongodb index for the variation collection in order to speed-up the access to the structural variants
{"collection": "variation", "fields": {"id": 1}, "options": {"background": true}}
{"collection": "variation", "fields": {"chromosome": 1, "start": 1, "end": 1}, "options": {"background": true}}
{"collection": "variation", "fields": {"_chunkIds": 1}, "options": {"background": true}}
+{"collection": "variation", "fields": {"chromosome": 1, "sv.ciStartLeft": 1, "sv.ciStartRight": 1, "sv.ciEndLeft": 1, "sv.ciEndRight": 1, "type": 1, "sv.type": 1}, "options": {"background": true, "sparse": true}}
{"collection": "variation", "fields": {"annotation.consequenceTypes.geneName": 1}, "options": {"background": true, "sparse": true}}
{"collection": "variation", "fields": {"annotation.consequenceTypes.geneId": 1}, "options": {"background": true, "sparse": true}}
{"collection": "variation", "fields": {"annotation.consequenceTypes.transcriptId": 1}, "options": {"background": true, "sparse": true}}
