Add Service chapter visibility control

[miroslavpojer]

• Clean up of action controls to manage service chapters visibility.
• Grouped "features" controls.
• Simplified the code using static ActionInputs.
• Introduced defaults values in ActionInputs and env variable access methods.
• Updated unit tests.

Closes #52

[miroslavpojer]

Release notes:

• Clean up of action controls to manage service chapters visibility.
• Grouped "features" controls.
• Simplified the code using static ActionInputs.
• Introduced defaults values in ActionInputs and env variable access methods.
• Updated unit tests.

[MobiTikula]

README.md
line 268: python3 ./<path-to-action-project-root>/main.py = I think there should be a dot before setting the path to action project root.
GENERATOR
line 20: from github import Github, Auth = extra Auth module

There are code formatting issues, but will be probably part of formatting issue.

[miroslavpojer]

README.md line 268: python3 ./<path-to-action-project-root>/main.py = I think there should be a dot before setting the path to action project root. GENERATOR line 20: from github import Github, Auth = extra Auth module

There are code formatting issues, but will be probably part of formatting issue.

README.md line 268: python3 ./<path-to-action-project-root>/main.py = I think there should be a dot before setting the path to action project root. GENERATOR line 20: from github import Github, Auth = extra Auth module

There are code formatting issues, but will be probably part of formatting issue.

Addressed in commit bb2e565.