Fixes issue #4050, making dualswords out of energy cutlass

New path for energy swords, /obj/item/weapon/melee/energy/sword/saber and the different type of colours (purple, red, green, blue) are childrens of it.
You can only use sabers to create a dualsword and to archieve the funky colours with the multitool.
Dualswords now will be eqipped on hand once created instead of staying on the floor.
Fixes issue #4050.