Email senders uniformization

Closes #87.

To close the issue is required to run updates on the DB and to run the script 'pt.utl.ist.scripts.runOnce.email.pt.utl.ist.scripts.runOnce.email.EmailSendersUniformization' from the Fenix scripts project.

For some of the senders the institution acronym is defined in 'net.sourceforge.fenixedu.domain.organizationalStructure.getInstitutionAcronym()' and so the value returned by this method should be updated so that it returns the desired institution acronym.