Add support for custom column mapping in primary key column

Add support for idInjection

Closes loopbackio#1

lib/mssql.js

@@ -392,11 +392,13 @@ MsSQL.prototype.buildInsert = function (model, data) {
   var params = [];
   var props = this._models[model].properties;
   var modelPKID = this.idName(model);
-  //remove the pkid column if it's in the data, since we're going to insert a
-  // new record, not update an existing one.
-  delete data[modelPKID];
-  //delete the hardcoded id property that jugglindb automatically creates
-  delete data.id;
+  if (props[modelPKID].idInjection !== false) {
+    //remove the pkid column if it's in the data, since we're going to insert a
+    // new record, not update an existing one.
+    delete data[modelPKID];
+    //delete the hardcoded id property that jugglindb automatically creates
+    delete data.id;
+  }
   Object.keys(data).forEach(function (key) {
     if (props[key]) {
       insertIntoFields.push(self.columnEscaped(model, key));
@@ -1167,8 +1169,14 @@ MsSQL.prototype.propertiesSQL = function(model) {
     if (prop === modelPKID) {
       var idProp = objModel.properties[modelPKID];
       if (idProp.type === Number) {
-        sql.push(self.columnEscaped(model, modelPKID) +
-          " [int] IDENTITY(1,1) NOT NULL");
+        if(idProp.generated !== false) {
+          sql.push(self.columnEscaped(model, modelPKID) +
+            " " + self.columnDataType(model, modelPKID) + " IDENTITY(1,1) NOT NULL");
+        }
+        else {
+          sql.push(self.columnEscaped(model, modelPKID) +
+            " " + self.columnDataType(model, modelPKID) + " NOT NULL");
+        }
         continue;
       } else if (idProp.type === String) {
         if(idProp.generated) {