Descarteslabs

Added
- Complex filtering expressions for image attributes

Fixes
- Raise explicitly on 409 response
- Keep retrying token refresh until token fully expired
- Fixed race condition when creating `.descarteslabs` directory

Added
- Added ext namespace
- Metadata multi-get

Fixes
- Fix OpenSSL install on OSX

Fixes
- Automatic retry on 504
- Internal API refactoring / improvements for Auth

Added
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* Add raster bands methods to metadata service.
* Deprecate raster band methods.
* Add require_bands param to derived bands search method.

Fixes
-------
* Test suite replaces original token when finished running script tests.

Added
- Support for derived bands endpoints.
- Direct access to `const_id` to `product` translation.

Fixes
- `descarteslabs` scripts on windows OS.

Fixes
- Fix auth login