US-5.1.2: Radius of gyration Rg and end-to-end distance R_ee

[Peariforme]

User Story

As an analyst, I want Rg and R_ee for polymer chains.

Acceptance Criteria

• Instantaneous and trajectory-averaged Rg
• R_ee and <R_ee^2>
• Ratio <R_ee^2> / <Rg^2> (theoretically 6 for ideal chain)
• Per-chain and ensemble average