(feat) Column Preference for Data Browser

[dblythy]

Closes #172.

With this PR, you can specify "columnPreference" in your app settings.

This can easily allow you to order and size specific columns consistently across multiple devices and classes.

"apps": [
    {
      "serverURL": "http://localhost:1338/parse",
      "appId": "hello",
      "masterKey": "world",
      "columnPreference" : {
        "_Role" : [
          {"name":"updatedAt","width":250,"visible":true}
        ],
        "_User" : [
          {"name":"objectId","width":150,"visible":true},
          {"name":"updatedAt","width":150,"visible":true},
          {"name":"createdAt","width":150,"visible":true},
          {"name":"firstName","width":150,"visible":true},
          {"name":"lastName","width":150,"visible":true}
        ]
      }
    }
  ],

The remaining fields will still display in the "Manage Columns" option, but will be invisible.

If a class isn't specified in columnPreference, the default is applied.

What this looks like:

Note that my "_User" class has about 20 fields, and without this set, it ends up an unordered, scrambled mess.

[dblythy]

This could also work towards closing #1497, with an option such as:

 "columnPreference" : {
        "_Role" : [
          {"name":"updatedAt","width":250,"visible":true, "preventSort":true}
        ],
        "_User" : [
          {"name":"objectId","width":150,"visible":true},
          {"name":"updatedAt","width":150,"visible":true},
          {"name":"createdAt","width":150,"visible":true},
          {"name":"firstName","width":150,"visible":true},
          {"name":"lastName","width":150,"visible":true, "preventSort":true}
        ]
      }

[davimacedo]

Nice! LGTM!

[Klaitos]

@dblythy I've made a proposal on your idea here #1709