Allow for specification of image category

add "sourceURL" in the config.ini file located in AppData/Local/Unsplash_GUI/ folder, which allows the user to specify image search category, e.g. "random" vs "featured" (syntax can be found at https://source.unsplash.com/). This option is currently not available in the GUI.

Also update to VS2015.

Dark Style UI

Applied Qt dark stylesheet from QDarkStylesheet (https://github.com/ColinDuquesnoy/QDarkStyleSheet)

Minor bug fix

Fixed a bug associated with detached monitors

Feature updates

Auto-save and load user's previous settings, and add the option to auto-start at system startup.
Hide the setting interface by default on system startup.

Implemented updated Windows API

Add support to set different different Wallpapers for different monitors (minimum system requirement: Win8).

GUI version

2.0

The GUI version and update of the ReadMe file

Non-GUI version

Use "UnsplashWallpaper.exe --help" to obtain detailed setting commands