Python API:
* Names of scene identifiers have been harmonized for consistency with the USGS API and the use of multiple datasets. `entity_id` and `display_id` are now used instead of `scene_id` and `product_id`, as those IDs may now refer to Landsat Collection 1, Landsat Collection 2, or Sentinel products.
* Metadata returned by `api.search()` and `api.metadata()` have been harmonized to be more consistent across the datasets. `entity_id`, `display_id`, `acquisition_date` and `cloud_cover` fields are always present regardless of the dataset. Camel case field names from the USGS API are converted to snake case for consistency (i.e. `acquisition_date` instead of `acquisitionDate`). Numeric fields are converted to integers or floats if possible, and dates are converted to Python datetimes.
CLI:
* `landsatxplore search` now prints the `display_id` instead of the `entity_id` by default.
* In `landsatxplore search`, `--output` option now accepts `entity_id` and `display_id` values instead of `scene_id` and `product_id`.
* Added a `--skip` flag to `landsatxplore download` to skip download and only print remote filename for testing purposes.