Minor fixes to windoors and display cases

Fixes:
* Emags shouldn't be caught in the ID check for unlocking display cases.
* Windoors can now be deconstructed after being emagged/when opened.
* Changed windoor and display case messages to use CSS classes for formatting.
* Some typos.

Display cases' code should probably be refactored into /obj/machinery. I'm working on making windoors powered (see issue #2165) but I won't add those commits here because of the feature freeze.