Support plan level dose engine parameters

[cpinter]

Some beam parameters should be plan-specific, so that they do not need to be changed in every beam individually. For the proton engine, these are the following: every parameter in the Beam model tab except for smearing radius, and the Source distance parameter in the Geometry tab.

Maybe instead of just implementing this option to specify whether a parameter is beam or plan specific, we can implement beam groups (a feature we discussed earlier) at the same time. Notes about this feature:

• Beam groups: plan contains one or more beam groups, a beam group contains one or more beams
• Properties defined for each beam group, which the contained beams share
  • Plugin dose engine
  • Isocenter
  • Target segment
  • Isocenter specification
• Rethink beam cloning

Migrated from https://app.assembla.com/spaces/slicerrt/tickets/863-support-plan-level-dose-engine-parameters/details