updates to SDR handbook
Moved SDR handbook to marketing handbook, combined BDR and SDR handbook onto /handbook/marketing/sdr and added links to them in the marketing main page.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Moved SDR handbook to marketing handbook, combined BDR and SDR handbook onto /handbook/marketing/sdr and added links to them in the marketing main page.