convert null to an empty map/set

We already do this for lists, it makes more things work without
downside that I can think of.

On the upside mongoDB can intentionally store nothing at all for the field
when then Set/Map is empty, saving disk space.
Version bump
Merge branch 'master' of github.com:yesodweb/persistent
Version bump
simplify embedded null handling

This may produce worse error messages.
However, it allows for non-existent fields in the case of
Maybe, List, Map, and Set.
Merge pull request #262 from yesodweb/embedded-null

simplify embedded null handling
use a single test runner
add embedded test cases
mongoDB: toInsertDoc: fix variable shadowing issue
fix haddock generation
mongoDB version bump
version bump persistent-template
toStrict is not in bytestring < 0.10

closes #263
Merge branch 'master' into persistent2

Conflicts:
	persistent-mongoDB/Database/Persist/MongoDB.hs
	persistent-mongoDB/persistent-mongoDB.cabal
	persistent-template/persistent-template.cabal
	persistent-test/EmbedTest.hs
	persistent-test/persistent-test.cabal
	persistent-test/test/main.hs
	persistent/persistent.cabal
fix SQL tests
Merge branch 'master' into persistent2