R1:23dc68604561

Conpherence - add per thread notification setting

Summary: Introduces a new settings panel for Conpherence specific settings.

Test Plan:
started a thread with a test user, thus two participants total. Replied to conpherence, toggling notification settings in between. Verified 1 or 2 emails were sent as appropos to the current toggle.

Toggled global setting and verified setting was updated in conpherences where nothing was specified. Verified setting conpherence setting overrides global setting.