FI-957: Build .index.json for package tarball or upload standalone profiles

[jason-crowley]

FI-957: This PR adds an IndexBuilder utility class to handle indexing IG packages (creating an .index.json at the root and for all subdirectories). It also POSTs profiles one-by-one to the validator if no package.json is present.

Submitter:

• This pull request describes why these changes were made
• Internal ticket for this PR: https://oncprojectracking.healthit.gov/support/browse/FI-957
• Internal ticket links to this PR
• Internal ticket is properly labeled (Community/Program)
• Internal ticket has a justification for its Community/Program label
• Code diff has been reviewed for extraneous/missing code
• Tests are included and test edge cases
• Tests/code quality metrics have been run locally and pass

Reviewer 1:

Name:

• Code is maintainable and reusable, reuses existing code and infrastructure
  where appropriate, and accomplishes the task's purpose
• The tests appropriately test the new code, including edge cases
• You have tried to break the code

Reviewer 2:

Name:

• Code is maintainable and reusable, reuses existing code and infrastructure
  where appropriate, and accomplishes the task's purpose
• The tests appropriately test the new code, including edge cases
• You have tried to break the code

[radamson]

Tested it out and works well with:

• just profiles
• profiles and package.json
• profiles, package.json and .index.json

Code looks good and clean too (thanks @Jammjammjamm and @jason-crowley!)