[CR] B12.0 Add Information Model Tasks to Release Plan

[jordanpadams]

Added to Release Plan:

• B12.0 Evolution of DD_Associate_External_Class pds4-information-model#368
  • multiple tasks associated with the GEOM LDD split efforts. this has required a significant amount of effort from @jshughes to support refactoring of the LDDTool / Information Model code for generating XSD / SCH.

Removed from Release Plan:

• Refactoring of IMTool pds4-information-model#306
  • the code sitting under the hood of IMTool needs some refactoring. not a critical task, but something we need to get to in the future

Rationale:
The GEOM LDD split effort is fully underway and we have pretty much dug the hole too deep at this point. Pulling back on that effort is most likely a non-starter, so we have to pivot to support that. The "B12.0 Refactoring of IMTool" effort is not critical and should not impact LDDTool for the near-term.

[jordanpadams]

Discussed, reviewed, and approved per SWG meeting on 7/20/21