Move metadata settings into its own object.

docs/metadata.rst

@@ -84,6 +84,10 @@ explanatory purposes.
             yulDetails: {}
           }
         },
+        metadata: {
+          // Reflects the setting used in the input json, defaults to false
+          useLiteralContent: true
+        }
         // Required for Solidity: File and name of the contract or library this
         // metadata is created for.
         compilationTarget: {
@@ -92,9 +96,7 @@ explanatory purposes.
         // Required for Solidity: Addresses for libraries used
         libraries: {
           "MyLib": "0x123123..."
-        },
-        // Reflects the setting used in the input json, defaults to false
-        "useLiteralContent": false
+        }
       },
       // Required: Generated information about the contract.
       output: