Add `where`, `isArray` and `clearChildren` options to () method (complete #8)

This allows us to use the `$clearCache()` method in the following ways:
```js
// clears all CommentsResource entries
CommentsResource.$clearCache()

// clears /?id=68 (2 methods)
CommentsResource.$clearCache({ where: [{ id: 68 }] })
CommentsResource.$clearCache({ where: { id: 68 } })

// clears only /array/?recent=true
CommentsResource.$clearCache({ where: { recent: true }, isArray: true, clearChildren: false })

// clears /array/?recent=true and all entries that belong to the array
CommentsResource.$clearCache({ where: { recent: true }, isArray: true, clearChildren: true })

// clears all CommentsResource entries except for /?id=68 (2 methods)
CommentsResource.$clearCache({ exceptFor: [{ id: 68 }] })
CommentsResource.$clearCache({ exceptFor: { id: 68 } })

// clears all CommentsResource entries except for /array/?recent=true and all entries that belong in which array
CommentsResource.$clearCache({ exceptFor: { recent: true }, isArray: true, clearChildren: false })

// clears all CommentsResource entries except for /array/?recent=true (but still clears all entries which belong in that array)
CommentsResource.$clearCache({ exceptFor: { recent: true }, isArray: true, clearChildren: true })
```

Tests for `where` added, tests for `exceptFor` are still working =)

**NOTE** This will break existing implementations, because:

BEFORE
```js
// clears all CommentsResource entries except for /?id=68
CommentsResource.$clearCache({ exceptFor: [{ id: 68 }] })

// clears all CommentsResource entries except for /array/?recent=true and all entries that belong to that array
CommentsResource.$clearCache({ exceptFor: { id: 68 } })
```

AFTER
```js
// clears all CommentsResource entries except for /?id=68 (2 methods)
CommentsResource.$clearCache({ exceptFor: [{ id: 68 }] })
CommentsResource.$clearCache({ exceptFor: { id: 68 } })

// clears all CommentsResource entries except for /array/?recent=true and all entries that belong to that array
CommentsResource.$clearCache({ exceptFor: { recent: true }, isArray: true })
```

**However**, we could add a polyfill for old `$clearAll()` method which would make it working for older implementations also. *with a deprecation log message too, ofcourse*