Merge remote-tracking branch 'upstream/master'
Fixed addressWithIMAPAddress for drafts with bad address in to/cc/bcc fields
Recognize multipart/signed content type
Updated to libetpan 35c5c939fe4d5d7072b1629638ee96f2e6a4bbd1
appending nil will not crash (#812)
MCUTF8() to have the same behavior as MCUTF8DESC()
Added extra parameters to attachment
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/objc/abstract/MCOAbstractPart.h
Merge pull request #815 from miximka/master

Add possibility to recognize multipart/signed messages
Renamed 'extra parameters' of MCAttachment to 'content type parameters'
Added 'message id auto-generated' flag
Merge pull request #814 from foxinushka/feature/attachment-extra-parameters

Added extra parameters to attachment
Merge pull request #805 from foxinushka/master

Fixed addressWithIMAPAddress for drafts with bad address in to/cc/bcc fields
Fixed default value of mMessageIDAutoGenerated
Fixed behavior of htmlForAbstractMultipartAlternative()
Merge pull request #818 from foxinushka/feature/message_id_autogenerated_flag

Added 'message id auto-generated' flag
Fixed #826: group all BODY[HEADER.FIELDS] (...)
Batch every 50 emails
Merge branch '826-headers'
Added clean html method to rendeder delegate