Create share link with full edit privileges

[dkocher]

When creating a public link share of a single file, also specify permissions 15 in the API request to give download/view/edit access. The public link share will actually be given permissions 3 (read and update) because create and delete permissions are not relevant for single file shares

https://doc.owncloud.com/server/next/developer_manual/core/apis/ocs-share-api.html#create-a-new-share