[#32] Rename fields according to Protobuf Style Guide

Signed-off-by: Stanislav Bogatyrev <stanislav@nspcc.ru>

container/types.proto

@@ -14,27 +14,27 @@ import "netmap/types.proto";
 // SHA256 hash of stable-marshalled container message.
 message Container {
     // OwnerID carries identifier of the container owner.
-  refs.OwnerID OwnerID = 1;
+  refs.OwnerID owner_id = 1;
 
     // Nonce is a 16 byte UUID, used to avoid collisions of container id.
-    bytes Nonce = 2;
+    bytes nonce = 2;
 
     // BasicACL contains access control rules for owner, system, others groups and
     // permission bits for bearer token and Extended ACL.
-    uint32 BasicACL = 3;
+    uint32 basic_acl = 3;
 
     // Attribute is a key-value pair of strings.
     message Attribute {
         // Key of immutable container attribute.
-        string Key = 1;
+        string key = 1;
 
         // Value of immutable container attribute.
-        string Value = 2;
+        string value = 2;
     }
 
     // Attributes define any immutable characteristics of container.
-  repeated Attribute Attributes = 4;
+  repeated Attribute attributes = 4;
 
     // Rules define storage policy for the object inside the container.
-    netmap.PlacementRule Rules = 5;
+    netmap.PlacementRule rules = 5;
 }