Consistency regarding where exception messages are put: in code vs. in resources file

[stakx]

Moq currently does both. Ideally, all exception / user messages that are currently hard-wired in code should be moved to the resources file; it doesn't make sense that only some messages should be localizable, but not others.

(As a last resort to unblock UWP, doing it the other way around, i.e. hardcoding everything and making it unlocalizable, is also possible, though clearly not too desirable; see discussion in #274.)