Transaction Fee Module (#1648)

* wip

* Split bytes fee charging and charging by amount into different traits.

* Move to edition 2018.

* Implemented charge fee traits for fees module.

* Implemented 'on_finalise' for fee module.

* Updated fees finalize impl.

* Renaming and documentation update.

* Added overflow & underflow check for fee calculation.

* Added mock and unit tests for fee module.

* More unit tests for fees module.

* Fixed srml-executive unit tests.

* Remove transaction base/bytes fee from balances module, fix unit tests.

* fix compile error

* Fixed unit test.

* Minor fixes.

* Bump spec version.

* Bump spec version.

* Updated fees module and runtime wasm.

* Fees module code style improvement; updated runtime wasm.

* Bump spec and impl version.

substrate/node/runtime/wasm/Cargo.lock

@@ -651,6 +651,7 @@ dependencies = [
  "srml-council 0.1.0",
  "srml-democracy 0.1.0",
  "srml-executive 0.1.0",
+ "srml-fees 0.1.0",
  "srml-grandpa 0.1.0",
  "srml-indices 0.1.0",
  "srml-session 0.1.0",
@@ -1349,6 +1350,7 @@ dependencies = [
  "sr-sandbox 0.1.0",
  "sr-std 0.1.0",
  "srml-balances 0.1.0",
+ "srml-fees 0.1.0",
  "srml-support 0.1.0",
  "srml-system 0.1.0",
  "srml-timestamp 0.1.0",
@@ -1402,6 +1404,22 @@ dependencies = [
  "srml-system 0.1.0",
 ]
 
+[[package]]
+name = "srml-fees"
+version = "0.1.0"
+dependencies = [
+ "hex-literal 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-codec 3.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-codec-derive 3.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.81 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-io 0.1.0",
+ "sr-primitives 0.1.0",
+ "sr-std 0.1.0",
+ "srml-support 0.1.0",
+ "srml-system 0.1.0",
+ "substrate-primitives 0.1.0",
+]
+
 [[package]]
 name = "srml-grandpa"
 version = "0.1.0"