Compile flag for AuthenticatorConfig (#628)

* Adds a compile flag for AuthenticatorConfig

The command can be disabled for authenticators that don't want users to
change their configuration.

* adds tool for calling Config

* std now implies config_command

* removes obsolete comment

libraries/opensk/Cargo.toml

@@ -36,8 +36,10 @@ features = ["alloc", "ecdh", "ecdsa"]
 optional = true
 
 [features]
+default = ["config_command", "with_ctap1"]
+config_command = []
 debug_ctap = []
-std = ["crypto/std", "persistent_store/std", "rand/std_rng"]
+std = ["crypto/std", "persistent_store/std", "rand/std_rng", "config_command"]
 with_ctap1 = ["crypto/with_ctap1"]
 vendor_hid = []
 fuzz = ["arbitrary", "std"]