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 adding navigation role to content tabs

UM-USElab/gradecraft-development,UM-USElab/gradecraft-development,zqian/gradecraft-development,UM-USElab/gradecraft-development,mkoon/gradecraft-development,UM-USElab/gradecraft-development,mkoon/gradecraft-development,peterkshultz/gradecraft-development,zqian/gradecraft-development,peterkshultz/gradecraft-development,peterkshultz/gradecraft-development,mkoon/gradecraft-development,zqian/gradecraft-development