rpc: refactor lib folder (#4836)

Closes https://github.com/tendermint/tendermint/issues/3857

Moves `lib/` folder to `jsonrpc/`.

Renames:

**packages**

`rpc` package -> `jsonrpc` package
`rpcclient` package -> `client` package
`rpcserver` package -> `server` package

**structs and interfaces**

```
JSONRPCClient to Client
JSONRPCRequestBatch to RequestBatch
JSONRPCCaller to Caller
```

**functions**

```
StartHTTPServer to Serve
StartHTTPAndTLSServer to ServeTLS

rpc/jsonrpc/client: rename NewURIClient to NewURI

NewJSONRPCClient to New
NewJSONRPCClientWithHTTPClient to NewWithHTTPClient
NewWSClient to NewWS
```

**misc**

- unexpose `ResponseWriterWrapper`
- remove unused http_params.go

rpc/jsonrpc/client/encode.go

@@ -0,0 +1,46 @@
+package client
+
+import (
+	"fmt"
+	"net/url"
+	"reflect"
+
+	amino "github.com/tendermint/go-amino"
+)
+
+func argsToURLValues(cdc *amino.Codec, args map[string]interface{}) (url.Values, error) {
+	values := make(url.Values)
+	if len(args) == 0 {
+		return values, nil
+	}
+
+	err := argsToJSON(cdc, args)
+	if err != nil {
+		return nil, err
+	}
+
+	for key, val := range args {
+		values.Set(key, val.(string))
+	}
+
+	return values, nil
+}
+
+func argsToJSON(cdc *amino.Codec, args map[string]interface{}) error {
+	for k, v := range args {
+		rt := reflect.TypeOf(v)
+		isByteSlice := rt.Kind() == reflect.Slice && rt.Elem().Kind() == reflect.Uint8
+		if isByteSlice {
+			bytes := reflect.ValueOf(v).Bytes()
+			args[k] = fmt.Sprintf("0x%X", bytes)
+			continue
+		}
+
+		data, err := cdc.MarshalJSON(v)
+		if err != nil {
+			return err
+		}
+		args[k] = string(data)
+	}
+	return nil
+}