Support Mackup (follow symlinks when saving preferences)

[mcavallo]

Mackup is a neat tool that allows to symlink config files for easy provisioning and syncing between computers.

Currently Gifox is not following symlinks when writing the preferences file at /Users/user/Library/Preferences/com.gifox.gifox.plist so its not possible to sync it's configuration using Mackup.

[iby]

This is a great feature. Will implement in one of the releases following the next major update. 👍