Added PlanOperation::getOperatorId()
Implement a simple copy interface for PlanOperations
Basing TableRangeView on const tables
Fix ctor of hashtable that excepts list of other tables
Adding task dependencies handles done dependencies

Before, adding a done observer to a task with the standard addDoneObserver()
method resulted in a dead lock if that task was already finished. Rather than
having a client check if a task is done before adding a dependency to it, this
is now encapsulated by the addDoneObserver() method.
Added Task successor/predecessor retrieval methods
Added Pipelining interfaces and examples
Performance data helper: Sorted operation durations
Fix test output on non-NUMA systems

The group committer will try to bind to the current NUMA-node no matter what.
This will fail on non-NUMA systems (read: the vagrant VM). Therefore, `make
test` will have a message on stderr intermingled in its output even if the test
is not failing. This is ugly.

I propose to fix this by only attempting to bind to a node, if there are
actually different nodes on the system. I found this to be the cleanest
solution.
Merge pull request #357 from kaihowl/pullrequest/fixtestoutput

Fix test output on non-NUMA systems
Merge pull request #316 from kaihowl/pullrequest/kh-pipelining

Pipelining + Necessary Changes