This will be useful to "restart" a scan when things go wrong in production. Another useful use case is to check reproducibility.

Warning:
If you intend to retry a failed scan, this option should be used only after checking that the error was transient and not caused by the scanner or its parameters.

Internal Changes:

• Added 2 DB collections
  1. for storing user's request info
  2. for storing i3 events (separated to avoid redundancy for rescanning)
• Updated rest-tools version; uses ArgumentHandler for argument validation

closes #121
closes #82