Multi-way join operators

[khgl]

Changes in this request includes:

• Hash and hybrid hypercube implementations
• Squall integration with Redis
• Squall integration with GraphiteConsumer.

[avitorovic]

I updated some code in the main epfldata/squall branch. Please first pull from the epfldata/squall and merge locally, then please send a separate pull request to https://github.com/epfldata/squall and https://github.com/avitorovic/squalltoaster. All the DBToaster code (due to a different license) should go to https://github.com/avitorovic/squalltoaster. Thanks!

[khgl]

I merged new changes and removed dbtoaster code / send separate pull request to the https://github.com/avitorovic/squalltoaster