GUI - added gray out functionality to all control buttons in the "Fields
to Export" area, added new functionality that removes column names
selected for export from the master list, added new functionality that
sorts the order of column names that are removed from the export list
and returned to the master list, added dummy LinkList instance to
implement master list column name removal and restore and sorting.
Merge branch 'master' of https://github.com/Mattb230/UTDSE4485