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rename *PlatForm to *Platform

write_members_to_file: is called with _lag_ instead of lag +1, as inside there was a "lag-1" call... that one removed from inside as well

write_sample_info changed to take the whole path as a parameter: so now we explicitly see the path in pipeline, plus we don't need to return it back.
same for write_obs_to_file

managed imports in obs files

removed a need of using samples.DaCycle=DaCycle (now it is only passed in the "initialize" function)

performed actions discussed in email #2
removed unused __str__ functions
a bit of ordering of the pipeline.py

made cleanup in tm5_obsoperator
changed functions names - part 1
removed empty Validate function in obs, as well as its call
removed empty Initialize function in dasystem, as well as its call in pipeline (it's still called in some main functions)

- reduced to one the two-command messages logging 
- removed unnecessary commas and brackets in tuples definition
- removed unused imports
- __str__ definition: changed print to return
- removed unused values attribution ("dummy = ...")
- formatted the code
- repaired bad indentation
- removed dummy returns ("return None")
- removed non-meaning body of baseclasses.optimizer.Localize()

DaSystem
DaPlatform
ObservationOperator

are now handled before the pipeline, from the das.py contents. This replaces the situation in which they were all 
constructed inside the pipeline based on rc-file items from the da.rc script. This now only serves to identify the 
cycle information, and no longer hold info about the platform, sampling model, and da system used inside a cycle.