overhaul serialization code

The implementation of each class' serialization/deserialization is no longer
passed within a macro. The implementation now lies within a template of form:

template <typename T, typename Stream, typename Operation>
inline static size_t SerializationOp(T thisPtr, Stream& s, Operation ser_action, int nType, int nVersion) {
    size_t nSerSize = 0;
    /* CODE */
    return nSerSize;
}

In cases when codepath should depend on whether or not we are just deserializing
(old fGetSize, fWrite, fRead flags) an additional clause can be used:
bool fRead = boost::is_same<Operation, CSerActionUnserialize>();

The IMPLEMENT_SERIALIZE macro will now be a freestanding clause added within
class' body (similiar to Qt's Q_OBJECT) to implement GetSerializeSize,
Serialize and Unserialize. These are now wrappers around
the "SerializationOp" template.

src/walletdb.h

@@ -55,11 +55,15 @@ public:
     }
 
     IMPLEMENT_SERIALIZE
-    (
-        READWRITE(this->nVersion);
-        nVersion = this->nVersion;
-        READWRITE(nCreateTime);
-    )
+
+    template <typename T, typename Stream, typename Operation>
+    inline static size_t SerializationOp(T thisPtr, Stream& s, Operation ser_action, int nType, int nVersion) {
+        size_t nSerSize = 0;
+        READWRITE(thisPtr->nVersion);
+        nVersion = thisPtr->nVersion;
+        READWRITE(thisPtr->nCreateTime);
+        return nSerSize;
+    }
 
     void SetNull()
     {