Fix reference to non-existent upgrade profile introduced in f69e83c.

(Also removed an unused import).
Monkey patch DexterityContent.__getattr__:

This is required to support dynamic lookup of schema-level default values for
fields in behaviors. It basically is a backport of this Dexterity 2.x fix:
https://github.com/plone/plone.dexterity/commit/dd491480b869bbe21ee50ef413c263705af7b170
Bump og.document upgrade step 2702 to 2703

in order to make room for the missing upgrade step
following in the next commit.
Add missing upgrade step to add IDocumentMetadata

behavior to opengever.document FTI.
Merge pull request #344 from 4teamwork/lg_missing_upgrade_step_for_metadata_extraction

Add missing upgrade step for metadata extraction
Fixed outdated profile versions for og.base:default and og.examplecontent:default.
Merge branch 'lg-fix-metadata-versions' into feature_public_trial

Conflicts:
	docs/HISTORY.txt
Cleanup: Tabs to spaces, indentation, general whitespace cleanup.
Refactor document overview and simplify it.
Merge pull request #290 from 4teamwork/lg-refactor-document-overview

Refactor document overview
Choose a different mail header date, since 1970... is default for DateTime and datetime (test results are nearly useless).
Add IDocumentMetadata behavior to ftw.mail.mail
Initialize metadata on mail.
Fill document_author metadata with fullname queried by email address (OGDS).
Upgrade step: initialize metadata on extisting mail instances
Init missing field values in existing mails. Test metadata upgrade step.
Implement setting default values for mail metadata.
Remove specific mail index methods (document_date, document_author, receipt_date, sortable_author).
Move title and message into the common fieldset / Move title at first position.
Refactor mail metadata tests.