Added new json benchmark templates.
PipeliningHashBuild. Half of it.

Can stream. Does not understand how to deal with incoming streams.
Added missing hash table input to chunk.
Added explicit PipelineUnion.

The usage of PipelineCollect became convoluted.
Almost working version. PipelinedUnion is malfunctioning.

* We had to change addDependency to also deal with dependencies
  that are already done and will not notify their observers anymore.
* PipelinedUnion is now malfunctioning with a double free on probably
  the operation data. gdb shows AbstractResource / Operation Data
  double free.
Pipelining works now.

The problem was that the same position list was used for multiple
pointer calculators. All of these freed the same list upon disposal.
That led to a double free. Issue has now been corrected by having new
positions lists for every chunk that is emitted.
Added failing test.
Passing multi-join test.
Adding mac dotfiles to gitignore
Added a non-pipelined multi-join test