[FIX] ACL in sessions and contributions

- Closes #1445
[FIX] Allow registrars to access/modify registrant
[FIX] Allow registrars to access/modify registrant
[IMP] MaKaC.common.Configuration -> indico.core.config

 * Solves some circular import issues too
[IMP] Default box-shadow values for Compass
[FIX] ACL in sessions and contributions

- Closes #1445
[FIX] Display the right protection banner
Merge branch 'v1.1'
[FTR] Added simple eTicket PDF generation with QRCode

Introduced new dependencies: PIL and qrcode
[FTR] Added eTicket download link option after registration
[FIX] Add qrcode dependencie to setup.py
[MIN] Code style fix in TicketToPDF class
[FIX] Check for non-mandatory fields in PDF
[FTR] Add e-ticket tab to registration setup

- Add enable/disable e-ticket button to tab
[IMP] Use flasks url_for instead of urlHandlers

+ minimal code style fixes
[FTR] Add e-ticket link to registration page
[IMP] Add icon to e-ticket download link
[FTR] Add e-ticket tab to manage registrant view

- Add e-ticket download link to the tab
- Add info about the ckeck in status to the tab
[FTR] Add e-ticket download link to the menu

- Add migration to update the menu object in
  the database
[FTR] Add functionality to send e-tickets by mail

- Extend e-mail interface with attachment option