OPENDJ-2092 OPENDJ-2093 Code cleanup

* src/main/java/org/opends/guitools/controlpanel/task/NewSchemaElementsTask.java
** Extract methods to use super type and factorize code
** Autorefactor'ed file + Reformat
** Minor code cleanup
** Use straight return
** Use interface instead of concrete class for local variable which are collections
** Use ternary operator
** Format javadoc

* src/main/java/org/opends/guitools/controlpanel/ui/NewAttributePanel.java
** Autorefactor'ed file + Reformat
** Minor code cleanup
** Use interface instead of concrete class for local variable which are collections
** Use ternary operator

* src/main/java/org/opends/guitools/controlpanel/util/Utilities.java
* src/main/java/org/opends/guitools/controlpanel/task/NewSchemaElementsTask.java
** Consequences of changes done in NewAttributePanel