docs(select): Updated ngOptions track by examples

Made the example shown consistent with the advice above it regarding not using
`select as` and `track by` in the same comprehension expression.  Also changed
references to `trackexpr` to `track by` since `trackexpr` is not defined
except in the examples.

Added filter + track by example for ngOptions

The documentation for ngRepeat includes such an example specifying the proper
order for filters and and "track by" clauses in the comprehension expression,
but these docs for ngOptions do not.

Author: SteveShaffer

src/ng/directive/select.js

@@ -42,9 +42,9 @@ var ngOptionsMinErr = minErr('ngOptions');
  * or property name (for object data sources) of the value within the collection. If a `track by` expression
  * is used, the result of that expression will be set as the value of the `option` and `select` elements.
  *
- * ### `select as` with `trackexpr`
+ * ### `select as` with `track by`
  *
- * Using `select as` together with `trackexpr` is not recommended. Reasoning:
+ * Using `select as` together with `track by` is not recommended. Reasoning:
  *
  * - Example: <select ng-options="item.subItem as item.label for item in values track by item.id" ng-model="selected">
  *   values: [{id: 1, label: 'aLabel', subItem: {name: 'aSubItem'}}, {id: 2, label: 'bLabel', subItem: {name: 'bSubItem'}}],
@@ -69,8 +69,10 @@ var ngOptionsMinErr = minErr('ngOptions');
  *   * for array data sources:
  *     * `label` **`for`** `value` **`in`** `array`
  *     * `select` **`as`** `label` **`for`** `value` **`in`** `array`
- *     * `label`  **`group by`** `group` **`for`** `value` **`in`** `array`
- *     * `select` **`as`** `label` **`group by`** `group` **`for`** `value` **`in`** `array` **`track by`** `trackexpr`
+ *     * `label` **`group by`** `group` **`for`** `value` **`in`** `array`
+ *     * `label` **`group by`** `group` **`for`** `value` **`in`** `array` **`track by`** `trackexpr`
+ *     * `label` **`for`** `value` **`in`** `array` | orderBy:`orderexpr` **`track by`** `trackexpr` 
+ *        (for including a filter with `track by`)
  *   * for object data sources:
  *     * `label` **`for (`**`key` **`,`** `value`**`) in`** `object`
  *     * `select` **`as`** `label` **`for (`**`key` **`,`** `value`**`) in`** `object`