Create daily or weekly insight digest email

Adds notification_frequency setting to Owners,
adds to DAO, Model and Interface.
Adds ability to set frequency on account page.
Adds mandrill template option to InsightsGenerator plugin for future.
Sends email after insights generation if user is an admin.
Generates email and subject from smarty template.
Added tests for insights generator plugin contoller.
Added tests for new owner features.
Added tests for crawl and email sending.