Improved logging using logback

Overhauled the logging system as described in #195
* Split the onscreen log ('app log') from the log.txt file ('file log') to allow more detail in the file log when needed
* Adds system information such as OS and Java version to the file log
* Logs full exception stack traces to the file log
* Added formatting to the app log so that important events like errors or match results have their own formatting
* Made the app log threadsafe so that multiple threads can write to it at once
* Allows for detailed debug logging to be enabled (by developers) in the logback.xml file
Added support for inbuilt OS X Notifications on Macs

Any Mac that supports OS X Notifications (ie Mountain Lion and later) now uses OS X Notifications instead of the custom notifications previously used.
Made OS X Notifications a configurable option

On OS X Mountain Lion and later, a new notifications style option is available which lets you pick between the original HearthStats notifications style or the built-in notifications of Mac OS X.
Fixed updater on OS X

The previous checkins for OS X Notifications broke the updater because the updater doesn't contain the necessary native libraries for OS X. I switched back to Java-only notifications for the updater.
Changed location of config and temporary files to be more Mac-friendly

In response to #177, I've moved all the locations of temporary files on OS X to a more Mac-friendly location: ~/Library/Application Support/HearthStatsUploader

I've also moved the config.ini file from the home folder to ~/Library/Preferences/net.hearthstats.HearthStatsUploader.ini. If you already had a config.ini file in your home folder then it will be migrated to the new location so that you don't lose your settings.
Merge pull request #215 from gtch/master

Improved logging and OS X Notifications support