Improvement and extra validation

Ensured defaultDescriptionFieldName in  EnumsField class is nullable.
Validation is done on all enum constants. An extra validation is also
added to getSettingByName method in SettingsUtilBase class
Improvement and extravalidation

Ensured that the getter method returned in SUBUtils does not have a void
return type.  Ensured that valid Number Strings are used as the default
values for the settingsEnums used for getSettingsXXXvalue(enum) methods.