Misc Issues for Email communication

[michellealva]

• Multiple threads getting create even if message/subject is same (crm.frappe.io)
• Drag and drop for cc/bcc to move them
• Do not create new deals/leads if someone from cc of the existing lead/deal replies. Append in the same thread.
• Email modification should reflect in the modified timestamp
• Add communication status feature in core
• Create lead from email in core