Bugfix: Make sure IDs in HTML are unique

Quick action button IDs were repeated in every row of the file table, 
which isn't allowed in HTML (IDs must be unique per document).
By changing to classes, this offense was resolved.

The same goes for IDs in the people shares part of the sidebar where IDs 
are now appended with the share ID, which is necessary since they need to be 
both unique and referenced by ID for accessibility reasons.

https://github.com/owncloud/web/pull/5028
https://github.com/owncloud/web/pull/5148
