Py-eodms-rapi

- Added download capability for SAR Toolbox orders.

- Fixed error regarding the `rapi_requests._rapi_url` variable.

- Removed batch searching of 1000 records (default `maxResults` now the same as the RAPI: 20 records).
- Added `first_result` to `search` method so user can still get all results using pagination (same functionality as [firstResult](../../wiki/Directly-Accessing-the-EODMS-REST-APIget-firstresult) in RAPI).
- Fixed `PREVIEW_AVAILABLE` filter for NAPL images.
- Streamlined parsing the filters for search requests (`EODMSRAPI._create_expr()`).

- Added method _submit_search_query to eodms.py
- Added method get_rapi_metadata to eodms.py which sends a request to https://www.eodms-sgdot.nrcan-rncan.gc.ca/wes/rapi/metadata
- Modified to allow access to RAPI without EODMS credentials

- Fixed issue with _check_auth in rapi_requests.py

- Added user-agent info to request headers
- Added a logout function to end EODMS sessions