Decrypt command was previously requiring that specified files have
in their paths the site name. This isn't necessarily always the case
for example we can have global files that need to be decrypted and do
not contain the site name in the filepath, but the site name is
relevant in ensuring based on the site-definition.yaml file that
pegleg uses the correct revision of the global repository.
The end result should be that when decrypting a file, we specify the
site name, pegleg ensures we're on correct revisions of the repos
and if the file exists, decrypt and print to stdout
This patch addresses this by:
1. Updating pegleg.engine.secrets.decrypt to no longer require a
site name.
2. Updating pegleg.cli.decrypt to no longer pass a site name to
pegleg.engine.secrets.decrypt
3. Updating documentation for CLI.
4. Updating unit tests for CLI and secrets.
Change-Id: Ia97518b06a58b069a4d6c0b8d68a37f45e5d31bb
fb5d54fdb9