Prefer forward secure and ECC cipher suites

I saw https://getsatisfaction.com/newsblur/topics/weak_crypto_available and realized a pull request might better communicate the ease in this improvement.

Configuration changes guided by https://community.qualys.com/blogs/securitylabs/2013/08/05/configuring-apache-nginx-and-openssl-for-forward-secrecy

Test results can be confirmed with https://www.ssllabs.com/ssltest/analyze.html?d=newsblur.com
Background sync service framework.
Replace old sync thread with sync service.
Option to disable background syncs.
Trim stories DB rather than wiping.
API to fetch unread hashes.
Refactor feed/folder/unread fetching into sync service.
Automatic syncing of new unreads in sync service.
Update unread status for older stories during sync.
Fix crash on missing user profiles.
Remove google reader import step from register workflow (#499)
Apply dark theme to divider item header.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	clients/android/NewsBlur/res/layout/activity_addsites.xml
Merge pull request #547 from manderson23/darktheme

Android: Apply dark theme to divider item header.
Cleanup when on feed/folder list, but not when reading.
Clean up stories per feed rather than globally.
Only clean up read stories.
Merge remote-tracking branch 'upstream/master'
Option to keep old read stories or not.
Remove unused function.