Configuration via environment variables

**Is your feature request related to a problem? Please describe.**
We have hundreds of different pipelines where we use DependencyCheck. When we want to disable a feature centrally, for example the Sonartype OSS Index, we need to change it in every single pipeline. It would be great if it was possible to read settings from environment variables in addition to CLI arguments / tool config. This would allow us to change it on the spot for everyone.

**Describe the solution you'd like**
In addition to existing options, read the config values from the environment. Example:
`--disableOssIndex` -> `DISABLE_OSS_INDEX = true`

**Describe alternatives you've considered**
Using a properties file is not as straightforward and simple to deploy, as it also needs to be adapted in every pipeline.

Thanks for providing this tool!