New logging system.

Logs are now stored under baseDir/Logs. The log files are stored as ATLauncher-Log_date.log. The date goes yyyy-MM-dd_HH-mm-ss.
Update changelog.
Merge pull request #111 from lexware/new-log-system

New log system
Add setting to only keep X days worth of logs and if older, clear them out
Remove old style logs if present
WooHoo 1,000 commits! Much milestone, such code, WOW! But anyway added in ImageIcon from theme
Download AuthLib, Guava and Log4J and classload them when the launcher starts. Used a snippet of FTB code found at https://github.com/Slowpoke101/FTBLaunch/blob/master/src/main/java/net/ftb/workers/AuthlibDLWorker.java
Update POM file so maven will actually work
Change download names when downloading launchers libraries to be more descriptive
Refactor the name of the authlib checking/adding to move it out to possibly more uses later on
Load external libraries from file
Beginning of Migration to AuthLib
Add some error checking into authentication
Enter button now edits/adds an account in the Account tab
Start of auth switching. My god it's a mess
I think this sorts out authentication, again needs ALOT of tidying up
Fix login issues when token is invalidated
Fix offline launching not working
Fix wild censoring of the console when offline
Fix old account info not being able to login