compiler: Move model-sources cfg to models.json

Remove `modelSources` option from `boot()` options, add `_meta.sources`
to `models.json`.

```json
{
  "_meta": {
    "sources": ["./custom/path/to/models"]
  },
  "Car": {
    "dataSource": "db"
  }
}
```

docs/configuration.md

@@ -165,7 +165,7 @@ All code samples are referring to the sample project described above.
 
   *models.json*
 
-  ```js
+  ```json
     {
       "car": {
         "dataSource": "db"
@@ -176,7 +176,6 @@ All code samples are referring to the sample project described above.
  2. Change per-model javascript files to export a function that adds
  custom methods to the model class.
 
-
   *models/car.js*
 
   ```js
@@ -188,18 +187,20 @@ All code samples are referring to the sample project described above.
     };
   ```
 
- 4. Modify the boot configuration to list the directory containing
-  model definitions.
+ 3. If your model definitions are not in `./models`, then add an entry
+  to `models.json` to specify the paths where to look for model definitions.
 
- ```js
-    var loopback = require('loopback');
-    var boot = require('loopback-boot');
+  *models.json*
 
-    var app = loopback();
-    boot(app, {
-     appRootDir: __dirname,
-     modelSources: ['./models']
-   });
+  ```json
+  {
+      "_meta": {
+        "sources": ["./custom/path/to/models"]
+      },
+      "Car": {
+        "dataSource": "db"
+      }
+  }
   ```
 
 #### Attaching built-in models

lib/compiler.js

@@ -42,9 +42,12 @@ module.exports = function compile(options) {
   // require directories
   var bootScripts = findScripts(path.join(appRootDir, 'boot'));
 
-  var modelSources = options.modelSources || ['./models'];
+  var modelsMeta = modelsConfig._meta || {};
+  delete modelsConfig._meta;
+
+  var modelSources = modelsMeta.sources || ['./models'];
   var modelInstructions = buildAllModelInstructions(
-    appRootDir, modelsConfig, modelSources);
+    modelsRootDir, modelsConfig, modelSources);
 
   return {
     app: appConfig,

test/compiler.test.js

@@ -267,17 +267,17 @@ describe('compiler', function() {
       });
     });
 
-    it('supports `modelSources` option', function() {
+    it('supports `sources` option in `models.json`', function() {
       appdir.createConfigFilesSync({}, {}, {
+        _meta: {
+          sources: ['./custom-models']
+        },
         Car: { dataSource: 'db' }
       });
       appdir.writeConfigFileSync('custom-models/car.json', { name: 'Car' });
       appdir.writeFileSync('custom-models/car.js', '');
 
-      var instructions = boot.compile({
-        appRootDir: appdir.PATH,
-        modelSources: ['./custom-models']
-      });
+      var instructions = boot.compile(appdir.PATH);
 
       expect(instructions.models).to.have.length(1);
       expect(instructions.models[0]).to.eql({