Added message to the UI when a user tries to update the nickname to an invalid one
Merge pull request #570 from AfonsoFGarcia/ticket/421647

Added message to the UI when a user tries to update the nickname to an invalid one
Minor improvments to letter of recommendation text.
added column with student's username
Merge pull request #556 from cbartol/ticket/rt#421209

Add students usernames in some interfaces
Allow grade submission to be done using either the student number either the username
we have to put the new elements into IndividualCandidacySeriesGradeSet when we add elements in the SelectedDegreesSet
Merge pull request #572 from cbartol/ticket/rt#421640

Fixed the error of removing a degree from the selected degrees
The problem is not when the degree is removed from the list. The problem is when we edit the selected degrees and add a new element, this new element is not added to the IndividualCandidacySeriesGradeSet. Thus when removing something that does not exist it throws an exception.
Bug fix: getting the element of the list the right way; formatted some
unreadable code
Bumped version for release of 3.7.4
Merge branch 'release/3.7.4' into develop
Bumped version for development after release.
Bug fix: it's necessary to pass this bean to the request before showing
the page, because it needs it
Minor change: added DEGREE as a possible degree type to choose
fixed condition when deleting a Unit
Merge pull request #574 from cbartol/develop

Fixed condition when deleting a Unit
Removed usages of JsonSimple from JerseyServices, fixed researchers export