Merge pull request #80 from thehyve/SESIDEV-157-Expiration-date-on-membership

Created module
Restructuring Main Menu.
Hide the Bootstrap Login/Register Form from main menu.
Changed description of sesi_og_email feature.
Moved and changed description of sesi_membership_mail feature.
Merge pull request #81 from thehyve/SESIDEV-109-registration-form-issue

SESIDEV 109 registration form issue
Made mail_sent field (on membership) no longer required, so it can be hidden without error messages.