Enhanced RDKit depiction

[timbernat]

A handful of visualization config and drawing settings would be desirable to include, particularly as it pertains to reaction fragments, namely:

• rdutils.reactions.reactions
  • Enhance R-group depiction
    • Add option to change “_displayLabel” on all likers to control Jupyter-based display
    • Add option on rxnfile write to set “_MolFileRLabel” (likely based on map numbers)
      • Deprecate awful, hacky string replacement of “*” with “R”
• rdutils.rdkdraw
  • Expand list of dynamically-accessible mol viz config settings (as is done here)