LILY-310: speedup historylist

- find emails and notes separate
- find emails by finding headers first
- make all emails in headers lowercase for fast search
- add index to header.name to speedup search
- fixed show more button
LILY-220: Add Archived mixin for model
LILY-347: Add default title in HistoryListItem with no subject
Prefetch related objects to reduce lazy lookups.
Fix south migrate (again) after the django upgrade.
LILY-349: fix emailtemplate bound to tenant
LILY-263: Increase font-size inbox mailbox subheader
merge branch 'fix/email-template-tenant-filter-349' into develop
Merge branch 'fix/improve-email-inbox-view-263' into develop
LILY-190: Improve entering recipients when composing an email
Merge branch 'feature/LILY-190-improve-entering-recipients-in-email-compose' into develop
LILY-344: split get_messages in batches of 500