Gatys multiresolution + GPU config

Added Multiresolution variant of the Gays method, which allows for higher quality results at the expense of more processing time.

Also implemented a configuration file to adjust the tile sizes based on GPU models.

The --tilesize parameter has been removed.

Alpha images bugfix

Solved a bug resulting in the loss of the alpha channel during the tiling method.

TGA and PSD formats

Added the ability to work with TGA and PSD images.

Tiling strategy + alpha channels

Any-resolution image processing through a tiling strategy.
Appropriate processing of alpha channels.

Multialgorithm implementation, refurbished user interface

Merge pull request #12 from albarji/feature/style-swap

Major overhaul of the application and addition of faster algorithms

Original interface

This is a tag created to keep a reachable version of the codebase following the user interface prior to October 2017