Fix unimplemented == operations

[mumencoder]

Fixes #2675

Problem

Comparing a number with a resource (e.g. 0 == 'sound/weapons/metalhit.ogg')
threw NotImplementedException: Equal comparison for 0 and '...' is not implemented
at runtime instead of evaluating to FALSE.

Fix

In DM, values of different types are never ==-equal, so each inner switch now
falls back to return false (mirroring the existing DreamResource/Appearance
branches) instead of throwing. This covers the whole class of cross-type
comparisons, and != / ~= inherit the fix since they route through IsEqual.

[wixoaGit]

In DM, values of different types are never ==-equal

If this is true then you could replace all these switches with an if (first.Type != second.Type) return false; early on in the method.