Fix gettext guidance violation
Fix gettext guidance violation

1. No string concatenation should be used in the gettext function.
2. Some extra parentheses should be used in coffee script, to avoid the following situation: in coffee script, the call ```gettext "text to be extracted" + "text should not be extracted"``` will be translated into ```gettext("text to be extracted" + "text should not be extracted")``` rather than ```gettext("text to be extracted") + "text should not be extracted"```.

bmedx/modulestore,bmedx/modulestore,bmedx/modulestore