Fix docstrings in base.multidoing

[jaelliot]

Fix RST/Sphinx docstring formatting warnings in src/hio/base/multidoing.py.

Changes:

• Normalize Parameters: / Returns: headings to Parameters:: / Returns:: with trailing blank lines
• Complete truncated parameter description in Crewer.__init__ (temp)
• Fix Bosser Attributes heading format
• Add missing blank lines after tojson Returns block

No logic or behavior changes — documentation only.