Move task, subtasks, and template directories under src

## Description
Now that wGulp is open source I'd like to clean up our repository by moving all source code under the `src` directory.

This should not introduce any functional changes.

## Testing
- Ensure tests pass
- Ensure wGulp projects like `react-tree` work as expected

@trentgrover-wf 
@evanweible-wf