Scala 2.11 compatibility.

- Fix Shape.copy type
- Remove val in ColumnExtensionMethods
- Convert \0 to \u0000
- Change TupleClass handling in SlickBackend
- Move ShapeLevel._ types to the top level to avoid diverging implicits
- Disambiguate PrimaryKey in AbstractSourceCodeGenerator
- Cross-build against Scala 2.10.3 and 2.11.0-M8
normalizes whitespace
migrates to 2.11.0-RC1 retaining cross-compat with 2.10.x

Since https://github.com/scala/scala/pull/3452 has been merged,
we've been running around offering easy upgrades. Here's little something
for slick.