Add License Processing Capability For CycloneDX Generated SBOMs

[REestwick]

When generating CycloneDX (JSON) SBOMs, license information is added in the form of a License ID, as following:

def get_license_from_name(name):
    return {'license': {'id': name}}

in file tern/tern/formats/cyclonedx/cyclonedx_common.py.

When this license information is not a valid SPDX license ID, as defined in the CycloneDX JSON Schema, it results in an invalid SBOM.

E.g. GPLv2+ (incorrect) as opposed to GPL-2.0+ (correct).

This proposed fix alters the get_license_from_name function to validate the name input as a valid SPDX license ID, utilising the spdx-license-list python module.

If this validation fails, the get_license_from_name function returns the license as a CycloneDX License Name, which can be any string.