Merge pull request #5 from mardiros/core_store

Use zope.interface for the index storage
handle recipient correctly in import_email module
remove thread_lookup from truncate list
a raw mail model and core object to store mail in binary format
Merge pull request #6 from mardiros/core_store

Rename id with full name
fix on column rename missed
be consistence RawMail id is raw_id column
store mail in RawMail
resolve users from smtp recipients
missing declarative pkey_name for RawMail
add resource API to view a raw mail
remove Response, use renderers
pep8 a bit
message and thread got a subject column in cassandra models
thread.subject also in index
add a PartRenderer that use part content_type
missing subject attribute on message and thread interfaces
store Content-Disposition part value