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  (requires recent StarPU to get them from platform_recdump)

handle communications, related to #19

Additional code to handle communications. Contains: 
- parsing logic to get information about handles required/produces by each task from `task.rec`
- change to availSequence to allow ALAP insertion
- CommSequence to handle comms, ItemManager to handle data availability
- new option `comms` in GreedyAlgorithm to activate all this

Notably missing: 
- better way to specify bandwidth (for now it is a global value with `--bw` option)
- for now default location for all initial items is memory node 0
- include this in (some) other algorithms

See merge request !4

New option for export in .rec format: choose between specifying the worker or all workers of this type