Add mcmmo.skills.salvage permission to plugin.yml

Fixes issue where players would have access to the Salvage child skill
by default.

Mentioned in #2075
MCPC+ is now known as Cauldron
Workaround a CB bug by tracking piston events

There is a bug in Craftbukkit that causes piston events to fire
multiple times. We need to keep track of the extend and retract events
to see which piston events should be processed.
Fix bugs with pistons

This commit improves piston tracking and fixes a couple of bugs with
block tracking.

Fixes #2043
Fix typo with XP_Modifier in tools.default.yml
Add full Repairable support in tools config files

You can now fully configure a tool to be repairable from the tools.yml
config files.

Adds Repair_MinimumLevel and Repair_XpMultiplier to tools.yml
Set a pretty repair material name in tools.yml

Adds #1863
Finish the tools.yml header
Add full Repairable support in armor config files

You can now fully configure armor to be repairable from the armor.yml
config files.

Adds Repair_MinimumLevel and Repair_XpMultiplier to armor.yml
Set a pretty repair material name in armor.yml

Adds #1863
Merge branch 'master' of https://github.com/mcMMO-Dev/mcMMO