Updates to prepare for some refactoring

Hello there!
I'm refactoring the project a bit in the coming days, in order to both improve the reliability of the project, since it has been quite a few long years since i created it, and while it does work, it does not represent the quality of the code i'm able to produce these days and to make it easier to extend the project with better functionality. So this is a small preparation for the probable V3 of the project, it may take a while, but it will be worth it. I'll be closing most most PR's while i refactor the code and add tests to guarantee the quality of the project.

Changes and new features of this version:

• Added a message confirmation if the user tries to "empty" their VDF using the button added in the last version
• Backup the user's VDF file to %appdata% before meddling with it, so if something goes wrong, you have some course of action
• Attempt to improve the handling of the temp_grid directory #121 #114 etc (It has been too long with this error, please report if it still happens, maybe i merged some code and forgot to update the release)
• Fix Grid images not being properly set because we forgot to set the appid for each game in the VDF file
• Add support for JPG's and JPEG'S because Steam never told us it could read these (thanks @DragRedSim for the tips)
• Improved tests on some of the internal libraries
• Updated dependencies to latest version

If you face bugs or have questions, head over to our subreddit at http://reddit.com/r/UWPHook or ping me at our issues or my Twitter. Please, also send the contents of the log file located in %appdata%/briano/uwphook/

This software is open-source under the MIT License.

If you like what i did with it and want to support me, you can cheer me up at my Twitter or pay me a coffee via Paypal, it will help me to continue to build amazing open source tools for you!

Thanks for your support, and game on!