Feature/185 filtering on usj

[kavitharaju]

• Implements #185
• Details of implementation
  • include_markers option in to_usj()
  • exclude_markers option in to_usj()
  • include_markers option in to_list(), keeping BCV unless overridden by exclude
  • exclude_markers option in to_list()
  • combine_text=True option in to_list() and to_usj()
  • Filter enums for groups of markers
    • BOOK_HEADERS
    • TITLES
    • COMMENTS
    • PARAGRAPHS
    • CHARACTERS
    • NOTES
    • STUDY_BIBLE
    • BCV
    • TEXT
• CLI changes for the new feature
• Tests for the new feature
• Documentation of the new feature
  • API usage demo in python document
  • README.md, adding a dedicated section and different usage examples