Does Article 1 of Directive 2003/96/EC preclude national tax relief for energy products used for thermal exhaust air treatment or does the directive not apply to such energy products pursuant to the second indent of Article 2(4)(b) of Directive 2003/96/EC because use for thermal exhaust air treatment is a purpose other than as motor fuels or as heating fuels and this therefore constitutes dual use of energy products within the meaning of that provision?