* Fixed app not resuming backup after closing and reopening the app
* Fixed cosmetic effect of backup button doesn't change state right away after pressing start backup
* Fixed grammar
* Fixed deep copy problem that cause incorrect asset count when backing up
* Format code
* Renamed multipart filed name 'files' to 'assetData'.
* Added an additional field name of 'thumbnailData' to multipart form.
* Implemented upload mechanism for thumbnail directly from the mobile client.
* Removed dead code
* Implemented a version checking mechanism.
