Add option to accept pre-downloaded replicate bagit as input

re: conversation with Hongsuda to recreate a previous run

changed milestone to %v0.0.1

added To Do enhancement suggestion labels

changed milestone to %v0.0.2

mentioned in issue #71 (closed)

changed milestone to %0.0.3

added Doing label and removed To Do label

assigned to @ghenry

changed milestone to %DSL2

added To Do label and removed Doing label

added Doing label and removed To Do label

changed milestone to %1.0.0

changed milestone to %0.0.3

mentioned in commit 04bbabd5

added Test label and removed Doing label

mentioned in merge request !42 (merged)

mentioned in commit d14cdf77

closed via merge request !42 (merged)