- adds command line args to specify upload target directories/directory pattern
- adds a command line arg to show variables that could be used in a directory
  pattern
- makes the legacy path accessible (i.e., can be used in the directory pattern)
- slighly modifies some variable names to make their purpose more clear
- fixes small typo
- makes script a bit more 'noisy' to let it tell what it does (should facilitate
  debugging; as some actions are more configurable it's desirable to have a bit
  more information about what is going on)

- read settings from config
- parse settings
- pass settings to upload script
- adjust messages used for reporting via GitHub PR comments

…nto configurable_upload_directory

- added new settings `metadata_prefix` and `tarball_prefix`
- added new settings for reporting about pull request download failures
- added missing settings for build permissions and reporting about no permissions