This pr fixes a small bug, which appears when using the Filter data type. The test added fails with

  src/PersistentTest.hs:87:3: 
  1) persistent Filter In
       uncaught exception: SqliteException
       SQLite3 returned ErrorError while attempting to perform prepare "SELECT \"id\", \"name\", \"age\", \"color\" FROM \"Person\" WHERE (\"name\" IN ?)": near "?": syntax error

The issue is that ? should be wrapped in ( ) or sqlite can't parse it.

There seems to be more issues related to the Filter data type. For example someone could write Filter PersonName (FilterValues ["a", "b"]) Eq which will also fail. An additional fix could be:

• Hide Filter from users so that it is a Opaque type. Users will have to use the combinators from Database.Persist
• make constuctors safer, so that ie Eq can only be combined with FilterValue and not FilterValues.

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• Bumped the version number
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