Support import and export workspaces (#18)

[imageslr]

Change-Id: Id01faefe723d8e3a37f4583b0364344da9882c68

Export JSON:

file content:

{
  "workspaceList": [
    {
      "windowId": null,
      "workspaceId": "workspace_z3ikko9x"
    },
    {
      "windowId": null,
      "workspaceId": "workspace_l3tpkwaf"
    },
    {
      "windowId": null,
      "workspaceId": "workspace_12311"
    }
  ],
  "workspaces": {
    "workspace_l3tpkwaf": {
      "color": "red",
      "id": "workspace_l3tpkwaf",
      "name": "123123123",
      "tabs": [
        {
          "url": "www.google.com"
        }
      ]
    },
    "workspace_12311": {
      "color": "red",
      "id": "workspace_l3tpkwaf",
      "name": "1xxxx",
      "tabs": [
        {
          "url": "www.google.com"
        }
      ]
    },
    "workspace_z3ikko9x": {
      "color": "grey",
      "id": "workspace_z3ikko9x",
      "name": "123",
      "tabs": [
        {
          "active": true,
          "title": "百度一下，你就知道",
          "url": "https://www.baidu.com/"
        },
        {
          "title": "google.com.hk/search?q=123&oq=123&gs_lcr",
          "url": "https://www.google.com.hk/search?q=123&oq=123&gs_lcrp=EgZjaHJvbWUqBggAEEUYOzIGCAAQRRg7MgYIARBFGDkyBggCEEUYQDIGCAMQRRg8MgYIBBBFGDzSAQc0NjFqMGo3qAIAsAIA&sourceid=chrome&ie=UTF-8"
        }
      ]
    }
  }
}