Need to update optional fields handling for cases with filesAnalyzed=true

[Alexander Yukhanov]

Starting with 2.2.2 the following fields are optional even if filesAnalyzed are true:

• https://spdx.github.io/spdx-spec/v2.2.2/package-information/#79-package-verification-code-field
• https://spdx.github.io/spdx-spec/v2.3/package-information/#714-all-licenses-information-from-files-field
• package files.

Today the library generate incorrect errors if those fields are omitted (e.g.
https://github.com/spdx/Spdx-Java-Library/blob/master/src/main/java/org/spdx/library/model/SpdxPackage.java#L631)

[Alexander Yukhanov]

Submitted #198 to fix it

[Gary O'Neall]

Fixed with PR #198