Fixed bug where disabling hardcore mode for specific skills didn't work

Fixes #1661
Minor changes to Tree Feller - use a HashSet, move comment

LinkedHashSet doesn't actually do anything for us - we were never using the consistent ordering it promises, and openjdk-7 doesn't even provide that consistent ordering. Better to just not use it.
Actually keep all weeks, not just from the past year

Week numbers are obviously the same every year, we need to check the
year as well as the week number to determine if we should keep the
backup file or not.
Fixed bug where party chat broke if the display name contained special characters

Fixes #1676
Fix config.yml formatting
Use Matcher.quoteReplacement here!

Fixes #1676 - for real this time
Minecraft handles block drop chances internally.

Fixes #1678
Merge branch 'master' into dev-1.7.2update