DATAMONGO-586 - Bump version numbers for feature branch.
DATAMONGO-586 - Initial commit.
DATAMONGO-586 - Fluent interface for AggregationPipeline, more tests.
DATAMONGO-586 - Added type safe versions for aggregation operations $match and $sort.
DATAMONGO-586 - Not null assertions + auto-prefix field in $unwind operation.
DATAMONGO-586 - Type safe impl for projections (first version).
DATAMONGO-586 - Support for $add and $substract in projection.
DATAMONGO-586 - First round of polish.

Fixed or added copyright headers where necessary. Added Tobias as author where necessary. Added @since tags to newly introduced classes and methods. Documented non-nullability of parameters. Polished test cases a bit.
DATAMONGO-586 - Further enhancements to Aggregation API.

Fixed parameter names in comments. Add static factory method. Implement basic aggregation operation join point. Implement match operation. Extracted ReferenceUtil. Created starting point of $group operation with _id field definition and $addToSet fields.
DATAMONGO-586 - Yet another round of polish.

Added Apache license headers where missing. Removed separate package. Reduced visibility of ReferenceUtil as it's internal use only. Fixed formatting.
DATAMONGO-586 - Polished aggregation integration tests for readability.