Remove object schema parsing in CommandDefinition

The only thing we now care about in CommandDefinition is the
"minimalRole" field. Everything else is a black-box which we just
forward to the server without any semantic parsing.

Also completely removed command visibility support since it no
longer applies to trait/component model.

BUG: 25841230
Change-Id: Ie8fff57ffada289caa7876c2a53150bb116fd65b
Reviewed-on: https://weave-review.googlesource.com/1617
Reviewed-by: Vitaly Buka <vitalybuka@google.com>
diff --git a/src/weave_unittest.cc b/src/weave_unittest.cc
index c2f1e8f..2e41852 100644
--- a/src/weave_unittest.cc
+++ b/src/weave_unittest.cc
@@ -72,7 +72,7 @@
     "base": {
       "reboot": {
         "minimalRole": "user",
-        "parameters": {"delay": "integer"},
+        "parameters": {"delay": {"type": "integer"}},
         "results": {}
       },
       "shutdown": {