resolves #53 when importing antora.yml, only remove the prerelease property on the bucket if value of prerelease key is null

resolves #53 when importing antora.yml, only remove prerelease property on bucket if value of prerelease key is null

resolves #54 preserve nav.origin property on bucket if scanned antora.yml file defines nav key

resolves #52 throw error if scanned antora.yml attempts to update identity of bucket to identity of existing bucket

resolves #52 throw error if scanned antora.yml attempts to update identity of bucket to identify of existing bucket

resolves #50 automatically clear npm_config_package and npm_config_yes environment variables when npm_command is exec

resolves #50 automatically clear npm_config_package and npm_config_yes env vars when npm_command is exec