#10: Fixed jqgrid reloading, course list dropdown
#11 Added validation of fields
#11 Added confirm the deletion
#11 Updated QuestionDto
#10: Added role required for access
#10: Fixed updating of modules
#10: Deletion of a unit with assigned parent is no longer possible
#10: Added many to many relation and service
Updated course-module relation in the UI, modified relation and dto services
#10: Added possibility to select multiple parent nodes, fixed reloading of modules
#11 Added UI for questions
#11 Changed display 'valid selection options' in question UI
#10: Relations are now deleted properly
#11 Fixed bug with adding 'Valid selection options' in Firefox
#10: Changed select style to match bootstrap
#10: Fixed default sorting of jqGrids
#10: Fixed the bug with reloading of grid, improved performance for larger data sets
#12 Refactor methods forming entities from dto in DtoFactoryService