Market item filtering improvements and other some minor improvements

* Can now filter market items by vocation, level, slot type, and depot items.
* Added new bitwise lib for handling flag operations.
* Can now get/set local player vocation/premium (TODO: spell list).

modules/corelib/bitwise.lua

@@ -0,0 +1,17 @@
+Bit = {}
+
+function Bit.bit(p)
+  return 2 ^ p
+end
+
+function Bit.hasBit(x, p)
+  return x % (p + p) >= p       
+end
+
+function Bit.setbit(x, p)
+  return Bit.hasBit(x, p) and x or x + p
+end
+
+function Bit.clearbit(x, p)
+  return Bit.hasBit(x, p) and x - p or x
+end