Rename Palette to FRAME (#4182)

* palette -> frame

* PALETTE, Palette -> FRAME

* Move folder pallete -> frame

* Update docs/Structure.adoc

Co-Authored-By: Benjamin Kampmann <ben.kampmann@googlemail.com>

* Update docs/README.adoc

Co-Authored-By: Benjamin Kampmann <ben.kampmann@googlemail.com>

* Update README.adoc

substrate/frame/system/rpc/runtime-api/src/lib.rs

@@ -0,0 +1,34 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Runtime API definition required by System RPC extensions.
+//!
+//! This API should be imported and implemented by the runtime,
+//! of a node that wants to use the custom RPC extension
+//! adding System access methods.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+sr_api::decl_runtime_apis! {
+	/// The API to query account nonce (aka transaction index).
+	pub trait AccountNonceApi<AccountId, Index> where
+		AccountId: codec::Codec,
+		Index: codec::Codec,
+	{
+		/// Get current account nonce of given `AccountId`.
+		fn account_nonce(account: AccountId) -> Index;
+	}
+}