A ton of file renaming to make the purpose of each file clearer.

renamed:    ../../resources/browserid-errors.js -> ../../resources/error-messages.js
renamed:    ../../resources/browserid-network.js -> ../../resources/network.js
renamed:    ../../resources/browserid-identities.js -> ../../resources/user.js
renamed:    ../../resources/browserid-wait.js -> ../../resources/wait-messages.js
renamed:    browserid-network_test.js -> network_unit_test.js
modified:   qunit.js
modified:   storage_unit_test.js
renamed:    browserid-identities_unit_test.js -> user_unit_test.js

Updated all other files/tests accordingly.