Annotation import for existing volumes

[mzur]

• New endpoint to create pending volume for existing volume (if metadata is present). Either "import annotations" or "import file labels". If a pending volume already exists, it is discarded and a new one is created.
• Assign project_id to first project the user and volume have in common and the user is admin of.
• Redirect to default import workflow for pending volume.
• Show import button with JS when new file was uploaded
• Show import button with PHP if view is opened
• Show only "import annotations" or "import file labels" if not both are present in metadata
• Show no button if none of the information is present in metadata
• Update manual.

Resolves #922