fastWorkflow build command issue: Command Signature classes are not generated properly.

[sanchit056]

Describe the bug

1. The Command Signature input fields do not have proper descriptions, examples, patterns or constraints.
2. The Command Signature output fields do not have proper descriptions, examples, patterns or constraints.
3. The plain utterances could be better by building it dynamically through giving it description and examples of input fields.
4. The Command Signature class is missing the docstring (doc), which could be generated dynamically.
5. Unused imports in the command files.
6. Don't put any imports in the Responsegenerator._process_command implementation.
7. Responsegenerator.call function is missing a docstring.