Add source directory, rename groupContribution class to fuel

[d-montgomery]

This includes some breaking changes and reorganization of files (last time I promise).

Breaking changes:

• Creation of a source directory. This is necessary for organization as we build toward including multi-component evaporation models within FuelLib.
• In FuelLib.py, the groupContribution class was renamed fuel. This was motivated by the fact that the class is much more than GCM. It provides a characterization of the fuel. All instances of groupContribution must now be called using the following:

  import FuelLib as fl
  # Old instance
  fuel = fl.groupContribution(<fuel_name>)
  # New instance
  fuel = fl.fuel(<fuel_name>)
  

  This does also makes the documentation more clear.

Path Management

• There is now a file FuelLib/paths.py that creates variables for the various paths. Any file that imports paths automatically imports the source directory.

[Copilot]

Pull Request Overview

This PR implements a major reorganization of the FuelLib codebase by creating a source directory and renaming the main class from groupContribution to fuel. The changes include centralized path management and updates to all affected files.

• Introduces a source directory containing the main source code files
• Renames the groupContribution class to fuel for clearer semantics
• Implements centralized path management through a new paths.py file

Reviewed Changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
source/FuelLib.py	Renamed class from groupContribution to fuel and updated path handling
source/Export4Pele.py	Updated class references and improved export functionality with metadata
source/Export4Converge.py	Updated class references and improved export functionality
paths.py	New centralized path management file
tutorials/*.py	Updated import paths and class references
tests/*.py	Updated import paths and class references
docs/*.rst	Updated documentation to reflect class rename and reorganization

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