Imap-tools

* Fixed BaseMailBox.append bug on flag_set=None
* Added MailBoxFolderManager.set readonly argument

* Added MailBoxFolderManager.subscribe method
* Deprecation: BaseMailBox.seen method are deprecated now, use flag method

* Fixed MessageFlags values - all system flags begin with "\\"
* Fixed BaseMailBox.flag, BaseMailBox.append, MailMessage.flags - now works with system/custom flags correctly, -upper()
* Added utils.clean_flags
* Moved message.MessageFlags -> consts.MailMessageFlags
* Moved folder.MailBoxFolderStatusOptions -> consts.MailBoxFolderStatusOptions
* Moved utils.SHORT_MONTH_NAMES -> consts.SHORT_MONTH_NAMES
* Renamed utils.cleaned_uid_set -> utils.clean_uids

* Fixed multiple encodings case bug at MailMessage.subject

* Fixed MailMessage.from_bytes - MailMessage.uid/flags parse errors
* Fixed utils.parse_email_date - parse bug on bad dates
* Breaking change: BaseMailBox.fetch miss_defect argument now is False by default, it will be removed soon
* Increased the email collection for tests

* Fixed MailAttachment.attachments - message/rfc822 forwarded messages not missing now