Update categories.php

replaced hardcoded:
CATEGORY SAVED	-->	COM_JEM_CATEGORY_SAVED
CATEGORY PUBLISHED -->		COM_JEM_CATEGORY_PUBLISHED
Select an item to publish -->	COM_JEM_SELECT_ITEM_TO_PUBLISH
Select an item to unpublish -->	COM_JEM_SELECT_ITEM_TO_UNPUBLISH
CATEGORY UNPUBLISHED -->COM_JEM_CATEGORY_UNPUBLISHED
Select an item to delete -->COM_JEM_SELECT_ITEM_TO_DELETE
EDITED BY ANOTHER ADMIN	-->COM_JEM_EDITED_BY_ANOTHER_ADMIN