Refactor package

[devangcx]

• [x] refactor index
• [x] Remove duplication in file_writers module
• [ ] Style vtkjs_helpper
• [ ] Alternative method for grouping
• [x] Refactor to make documentation look right
• [ ] General refactoring direction

[devangcx]

https://github.com/ladybug-tools/honeybee-vtk/pull/100 makes this void.