Add more API functions

[normanrz]

Here is a list of API calls, that the webknossos should provide:

• List teams: GET /api/v5/teams Returns:

[{
    "id": "myTeamId",
    "name": "myTeamName",
    "organization": "myOrganizationName"
}, ...]

• Create a new team: POST /api/v5/teams with json body like {"name": "myTeamName"} (returns 400 if team name already in use)

• List users GET /api/v5/users

• Assign team roles to a user PATCH /api/v5/users/:id with json body like { "teams": [ {"id":"aTeamId", "isTeamManager": false}, ...] } (always send full list)

• Explore and add new datasets POST /api/v5/datasets/exploreAndAddRemote with a JSON body:

{
    "datasetName": '...',
    "remoteUri": 'file:///home/...',
    "folderPath": "/Datasets/"
}