Extend continuous absorption implicit capture to DDMC.

[RyanWollaeger]

Background

• Continuous absorption (variance reduction) was recently added to IMC by @alexrlongne and currently couples to analog DDMC.
• DDMC can employ continuous absorption by using the time elapsed during a particle step.

Description of Changes

• Extend continuous absorption implicit capture to DDMC.

Checklist

• New features are documented
• Tests added for bug fixes and new features
• (@lanl.gov employees) Update copyright on changed files

[RyanWollaeger]

Missed one modification to the DDMC CDF - this should be fixed now.

[RyanWollaeger]

@alexrlongne also reviewed this and approved - will go ahead and merge it.