Config class in trainer

[thibaultdvx]

Training config classes:

• Changes BaseTaskConfig to a TrainingConfig class and puts it in trainer folder.
• Splits TrainingConfig in several sub config classes.
• Makes classification, regression and reconstruction config classes inherit from TrainingConfig.
• Changes unittests to test those new config classes.

Trainer:

• Makes the Trainer use TrainingConfig.
• Removes some elements from MAPSManager and puts them in Trainer.

Random Search:

• Creates a RandomSearchConfig class.
• Makes classification and regression config classes specific to Random Search (but they inherit from the base classification and regression classes).
• Makes unittests for Random Search config classes.

CLI:

• Changes CLI options to connect them to those new config classes.
• Changes CLI main functions (in classification, regression, reconstruction, from_json, random-search and resume) to have something close to API mode and match modifications made in Trainer.

Organization:

• Moves some files from tasks folder to trainer folder.
• Renames some files.

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Futur works:

• Create a Random Search class to handle more easily the pipeline.
• Simplify resume CLI/API.

[thibaultdvx]

I just rebased @camillebrianceau, if it's ok for you I'll merge as soon as CI checks are ok