BlockBed.cpp: Fixed Multiple people in one bed.

OnUse in BlockBed.cpp now checks whether bit flag 0x4 in the Data values of the bed is set before somebody can try to sleep in the bed.
BlockBed.cpp: Fixed space at if statement

Added a space after an if statement and before the first bracket to keep up code conventions.
Add 'Meta < 3' to Cauldron
Add Hay Bale to Burnable
Add Light weighted pressure plates
Add Pressure Plate Sound
Disabled the leak finder.
Add Wolf Heal with Food
Fix Cauldron
Remove typeinfo import in IncrementalRedstoneSimulator
Merge pull request #702 from TheJumper/master

BlockBed.cpp: Fixed Multiple people in one bed.
Bad UTF-8 o.O
Merge pull request #704 from Howaner/GlobalFixes

Global fixes
Removed problematic utf8.
cClientHandle manages the client-registered plugin channels.

Fixes #706.
APIDump: Documented cClientHandle:HasPluginChannel.
Added cBlockArea:GetSize() and :GetOrigin() to Lua API.

These don't have a direct C++ equivalent, but are rather useful for the plugins.
Added cBlockArea::GetVolume, exported to Lua API.
Documented cBlockArea:GetOrigin(), :GetSize() and :GetVolume().
Updated CONTRIBUTING file with formatting and essential rules.