Updates to notif channel blocking UI

- Ensure 'see more' and 'done' buttons are always visible in landscape
- Since the channel list is now scrollable for the above, include all
channels that have sent a notification in the last 2 weeks, and all the
blocked channels
- Group channels by channel group, order alphabetically in a group
- do some cleanup of 'channel set', which hasn't been used for a long
time (if you long press on a summary with children with multiple
channels we just expand the group)

Test: ChannelEditorDialogControllerTest
Test: NotificationInfoTest
Test: PartialConversationInfoTest
Test: PreferencesHelperTest
Test: NotificationGutsManagerTest
Test: Make display and text as big as possible, and view dialog in
portrait and landscape on apps that have 1, 3, many channels
Fixes: 292179820

Change-Id: If8734723d6cbc0b0ac6dd6fae0e4924b48b6768a