Support for uri_decode_auth in MongoClient connections

Adds support for encoded usernames and passwords in config.connections objects. Add `uri_decode_auth: true` to your connection to enable.

example: **config/env/development.js**
```javascript
module.exports = {

  models: {
    connection: 'mongoDb'
  },

  connections: {
    mongoDb: {
      adapter: 'sails-mongo',
      host: 'localhost',
      port: 27017,
      database: 'yourDb'

      // Possible to add encoded symbols to the user as well
      user: 'yourUser',
      
      // Replacing @ with %40 to ensure connection string integrity
      password: 'your%40%40Pass', // will decode to: your@@Pass
      
      // New option to tell the underlying MongoClient#connect call 
      // that we've got credentials that need decoding
      uri_decode_auth: true,
    }
  }
}
```