Reworked TableEntryEditor tree generation & more

Tree node generation in TableEntryEditor reworked and simplified,
allowing for the removal of the various, nearly identical static
GenerateTreeNode functions in most parser classes, leaving only the
function in the EquipItemParser in modified form; changed some
properties and descriptions in EquipItemParser to be more accurate after
some testing, namely Item Effects (formerly Item Type), Group, Attack
and Defense; also some minor housekeeping, etc.