Fix maximum capacity for server simulation

[Bachibouzouk]

The maximum cap parameter triggers errors when implemented form the simulation server. This is an attempt to fix the problems

Changes proposed in this pull request:

• OPTIMIZED_ADD_CAP replaced by "optimized_add_cap" in the assets keys returned to EPA after simulating
• The if statement for adapting MAXIMUM_CAP for non-dispatchable production assets is now based on the value of DISPATCHABILITY and not on the existence of the key FILENAME in the asset_dict
• "maximum_add_cap" to the keys returned to EPA after simulating got production assets

The following steps were realized, as well (if applies):

• [ ] Use in-line comments to explain your code
• [ ] Write docstrings to your code (example docstring)
• [ ] For new functionalities: Explain in readthedocs
• [ ] Write test(s) for your new patch of code (pytests, assertion debug messages)
• [ ] Update the CHANGELOG.md
• [x] Apply black (black . --exclude docs/)
• [ ] Check if benchmark tests pass locally (EXECUTE_TESTS_ON=master pytest)

Please mark above checkboxes as following:

• [ ] Open
• [x] Done

:x: Check not applicable to this PR

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