Fixed #612

* Chests send contents updates to client
Fixed #627

- Attack() is now called from cAggressive instead of cMonster
* Monsters can no longer attack through walls
* Should fix last remnants of player damage after teleporting (that both
STR and bearbin contributed fixes to :P)
Fixed #190

+ Hoppers now collect pickups above them
Improved pressure plates

+ Two (or more) pressure plates can be triggered at the same time
* Fixed issues caused by pressure plates not being in the sources list
Simplified Attack() tracing
Made player jump reset less ambiguous
Changed inheritance a bit

* cBlockEntityWithItems now inherits from cBlockEntityWindowOwner
Removed some unneeded BroadcastWholeWindow()s
Added more missing GetClassStatic()s
Fancy stuff with constant references
Added proper debug messages
Removed debug messages again
Fixed typographical error
Merge pull request #664 from mc-server/generalfixes

General fixes