inbo/grtsdb: Version 0.2

# grtsdb 0.2

* Add a vignette on the basic usage.
* Added a `NEWS.md` file to track changes to the package.
* New features `add_legacy_site()`, `drop_legacy_sites()` and
  `extract_legacy_sample()`.
  These functions improve the ranking of legacy sites.
* Bugfix when restoring a compacted database (#2).