It fixes #244

It adds a new endpoint to retrieve statistics about the electronic logbook usage. Endpoint is:

/logbook/{sessionId}/stats?startDate=2019-01-01&endDate=2021-01-01

It returns:

[
{
"_id": {
"instrumentName": "id10",
"investigationId": 273270195,
"investigationName": "IH-HC-3553",
"category": "notification"
},
"count": 109,
"investigationId": 273270195,
"title": "Study of fast dynamics in Ralaxors",
"parameters": {
"__fileCount": "8362",
"__volume": "350528191194",
"__datasetCount": "55",
"__sampleCount": "45",
"__elapsedTime": "0",
"Id": "90763",
"IsCancelled": "false"
},
"startDate": "2020-10-09T08:00:00.000+02:00",
"endDate": "2020-10-14T08:00:00.000+02:00"
},
]

where count is the number of events for each category