abci: remove fee (#2043)

Refs #1861

We don't use the fee field and its likely just confusing.

We can add backwards compatible priority (instead of fee) later.

Note priority is better than fee because it lets the app do the math on how to rank order transactions, rather than forcing that into tendermint (ie. if we return fee, priority would be fee/gas)

docs/app-dev/abci-spec.md

@@ -186,7 +186,6 @@ See below for more details on the message types and how they are used.
   - `GasUsed (int64)`: Amount of gas consumed by transaction.
   - `Tags ([]cmn.KVPair)`: Key-Value tags for filtering and indexing
     transactions (eg. by account).
-  - `Fee (cmn.KI64Pair)`: Fee paid for the transaction.
 - **Usage**: Validate a mempool transaction, prior to broadcasting
   or proposing. CheckTx should perform stateful but light-weight
   checks of the validity of the transaction (like checking signatures
@@ -223,7 +222,6 @@ See below for more details on the message types and how they are used.
   - `GasUsed (int64)`: Amount of gas consumed by transaction.
   - `Tags ([]cmn.KVPair)`: Key-Value tags for filtering and indexing
     transactions (eg. by account).
-  - `Fee (cmn.KI64Pair)`: Fee paid for the transaction.
 - **Usage**:
   - Deliver a transaction to be executed in full by the application.
     If the transaction is valid, returns CodeType.OK.

docs/app-dev/getting-started.md

@@ -93,9 +93,7 @@ like:
   "jsonrpc": "2.0",
   "id": "",
   "result": {
-    "check_tx": {
-      "fee": {}
-    },
+    "check_tx": {},
     "deliver_tx": {
       "tags": [
         {
@@ -106,8 +104,7 @@ like:
           "key": "YXBwLmtleQ==",
           "value": "YWJjZA=="
         }
-      ],
-      "fee": {}
+      ]
     },
     "hash": "9DF66553F98DE3C26E3C3317A3E4CED54F714E39",
     "height": 14
@@ -219,13 +216,10 @@ the number `1`. If instead, we try to send a `5`, we get an error:
   "jsonrpc": "2.0",
   "id": "",
   "result": {
-    "check_tx": {
-      "fee": {}
-    },
+    "check_tx": {},
     "deliver_tx": {
       "code": 2,
-      "log": "Invalid nonce. Expected 1, got 5",
-      "fee": {}
+      "log": "Invalid nonce. Expected 1, got 5"
     },
     "hash": "33B93DFF98749B0D6996A70F64071347060DC19C",
     "height": 34
@@ -241,12 +235,8 @@ But if we send a `1`, it works again:
   "jsonrpc": "2.0",
   "id": "",
   "result": {
-    "check_tx": {
-      "fee": {}
-    },
-    "deliver_tx": {
-      "fee": {}
-    },
+    "check_tx": {},
+    "deliver_tx": {},
     "hash": "F17854A977F6FA7EEA1BD758E296710B86F72F3D",
     "height": 60
   }