stem remote.py defaults to plain text instead of GZIP

remote.py defaults no compression

387:    elif compression is None:
388:      compression = [Compression.PLAINTEXT]

399:      if not compression:
400:        compression = [Compression.PLAINTEXT]

instead the best available compression algorithms should be discovered and attempted

GZIP will almost always be available and is far better than PLAINTEXT

a warning should be written to stderr when compression fall backs

1. default case falls back to PLAINTEXT
2. requested ZSTD or LZMA falls back to GZIP or PLAINTEXT

download_descriptor.py should support a command parameter to choose compression type