Fix useNativeTypes handling.

- Fix previous useNativeTypes change.
- Refactor to make code easier to follow.
  - Performance change not tested.
- Handle another case for integeres similar to that from fromRdf#t0027.
  - Additions proposed for API test suite.

Author: davidlehn

lib/fromRdf.js

@@ -354,25 +354,25 @@ function _RDFToObject(o, useNativeTypes, rdfDirection, options) {
           rval['@value'] = true;
         } else if(rval['@value'] === 'false' || rval['@value'] === '0') {
           rval['@value'] = false;
-        } else if(rval['@value'] === 'True' || rval['@value'] === 'False') {
+        } else {
           rval['@type'] = type;
         }
-      } else if(types.isNumeric(rval['@value'])) {
-        if(type === XSD_INTEGER) {
+      } else if(type === XSD_INTEGER) {
+        if(types.isNumeric(rval['@value'])) {
           const i = parseInt(rval['@value'], 10);
           if(i.toFixed(0) === rval['@value']) {
             rval['@value'] = i;
           }
-        } else if(type === XSD_DOUBLE) {
-          rval['@value'] = parseFloat(rval['@value']);
+        } else {
+          rval['@type'] = type;
         }
       } else if(type === XSD_DOUBLE) {
-        // if not numeric and double, include type
-        // occurs for valid strings such as "+INF", "-INF", and large values
-        rval['@type'] = type;
-      }
-      // do not add native type
-      if(![XSD_BOOLEAN, XSD_INTEGER, XSD_DOUBLE, XSD_STRING].includes(type)) {
+        if(types.isNumeric(rval['@value'])) {
+          rval['@value'] = parseFloat(rval['@value']);
+        } else {
+          rval['@type'] = type;
+        }
+      } else {
         rval['@type'] = type;
       }
     } else if(rdfDirection === 'i18n-datatype' &&