Multiple enhancements and fixes to minecarts

+ They are destroyed instantly by creative mode
* Physics is much improved
+ Basic implementation of powered rails

src/BlockID.cpp

@@ -767,6 +767,7 @@ public:
 		g_BlockIsSolid[E_BLOCK_MELON_STEM]            = false;
 		g_BlockIsSolid[E_BLOCK_NETHER_PORTAL]         = false;
 		g_BlockIsSolid[E_BLOCK_PISTON_EXTENSION]      = false;
+		g_BlockIsSolid[E_BLOCK_POWERED_RAIL]          = false;
 		g_BlockIsSolid[E_BLOCK_RAIL]                  = false;
 		g_BlockIsSolid[E_BLOCK_REDSTONE_TORCH_OFF]    = false;
 		g_BlockIsSolid[E_BLOCK_REDSTONE_TORCH_ON]     = false;