Simplify the calcuation of the container for a collection of tiddlers

Fix #62

The general idea here is a Tiddlers Collection can now have a
bag or recipe attribute which contains the name or the bag or
recipe that is the container for these tiddlers. They default to
None.

This is _very_ useful information in serializations, making it so
that you don't have to appeal to the contained tiddlers or the
wsgi routing args to figure out what we're. Which saves processing
and guesswork.
Set bag or recipe on a tiddler revisions container.

Not actively used, but should be there for completeness.
Update some other copyright dates

see d6376686d3a1da6dcebee4397e215e2dcd4af843

that is, indeed, a long ass time
remove redundant global call

This is a carryover from previous experimentation with logging
wherein the LOGGER might get reassigned.
remove some redundancy by providing a check_incoming_etag

Looks at the incoming etag string and raises 304 if it matches
the expected etag string.
Further use of check_incoming_etag

Basically anywhere there is a etag check with a 304 raise.
pep8
Merge branch 'master' into generic-revisions