Notification on access request

Access Request notifications

• should be send by email to requester and data owner
• should include for data owner the URL to grant or decline access
• should be shown in notifications tab
• should be auto-deleted after 2 or 4 weeks OR have a "resend request" function
• should include a text field for a message from requester to data owner
• send distinct emails with distinct text to curators w/o link
• change email text footer to: "Archiving, sharing and discussing research data on Eastern Europe, South Caucasus and Central Asia"
• limit time of access, provide choices dropdown (2 weeks, 6 months, a year, unlimited) with 6 months as default

see #437 (closed) and #421 (closed)