Type checking on IDs

PlaneShift has many different kinds of IDs.  Currently, these are simply typed as "int" or "unsigned int" and given enlightening names like "id", "owner id", or the like - which certainly don't clarify which kind of ID one is dealing with.  It's easy to mix them up, and we've had several recent bugs caused by a developer doing so.

By creating distinct ID types, we can not only document what kind of ID is in use, but also allow the compiler to statically type-check ID usage - killing an entire class of bugs, and making the project more maintainable.

The following patch creates distinct ID types for PID, EID, and AccountID - more can come in future patches once this is in trunk.  You'll find the definition and associated operations in psconst.h.

Additional changes in this patch:
================================
* It fixes two bugs:
  - actionmanager.cpp/"Access is denied." - use of AccountID where a ClientID should go.
  - adminmanager.cpp/LIGHTNING - use of EID where a ClientID should go.

* It exposes an EID/PID mismatch in EntityManager::CreatePet (which cannot possibly work), but simply returns NULL instead of attempting to fix it.  AFAIK, pets are currently unused - only familiars, which have separate (but similar) code.

* It changes NPCClient to use 0 as an invalid ID, rather than (size_t) -1, for consistency.

Methods on ID Types:
====================
- IsValid(): 0 is considered invalid (most code already assumed this)
- Show(): returns a csString like "EID:12345", so our output messages always indicate the type of ID.
- Unbox(): returns the underlying integer (say, for passing to a DB query).  Think twice before using this.
- Operators ==, !=, <.

[Kayden, 2008-10-14 18:51:47]

Added some comments from IRC to put them on the official record. :)

http://codereview.appspot.com/7470/diff/1/104
File src/client/cmdusers.cpp (right):

http://codereview.appspot.com/7470/diff/1/104#newcode636
Line 636: options.Format("eid:%u",
psengine->GetCharManager()->GetTarget()->GetEID().Unbox());
I only used Show() for user readable messages, but left this using Unbox(). 
This way, someone could change how Show() displays without breaking the server.

Ragnarin suggests I should make a Read() or Scan() method for doing the inverse
of Show(), and make both sides use those.  That way, they'd stay in sync.

http://codereview.appspot.com/7470/diff/1/91
File src/client/gui/pawscontainerdescwindow.cpp (left):

http://codereview.appspot.com/7470/diff/1/91#oldcode109
Line 109: sigData.Format("invslot_%d", mesg.containerID * 100 + mesg.slotID +
16);
Ragnarin says this code is incredibly ugly.  And it is!

As I recall, container IDs mean the following:
< 0 = an enumeration (CONTAINER_EXCHANGE_OFFERING etc.)
< 1000 = an inventory slot ID (container in bulk inventory)
>= 10000 = an EID (container in the world)

I didn't attempt to clean up Vengeance's container mess.  It's worth doing, but
is dangerous and a big job in and of itself.  I feel we should come up with a
new user interface for inventory and crafting first, which would necessitate
changes here.