Filehandlers

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* Refactored documentation

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+ Added FileManipulator.load_from_json method
Lots of documentation fixes

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+ Added FileManipulator.delete method
- Removed AbstractFile.change_file_name

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* We are now using Semver
+ Added AbstractFile.exists method

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+ Added FileManipulator.get_file_contents_singlestring method

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+ Added contributing guidelines.
+ Added OpenModes enum.
* Made files that remained open close themselves (prevents memory leaks).
+ Added FileManipulator.write_to_file method.