Wishlist for xml modifying functions

[janssenhenning]

Here some ideas for useful xml modifying functions beyond the ones available are collected.

• Creating a new kPointList tag from an array (or some general datastructure) of values (not an aiida node)
• Switching the used kPointset with some checks that the given point set is available and maybe compatible
• create a copy of a species with new name to be able to break symmetries (maybe not necessary for aiida but it could be useful for someone using these routines directly)

[janssenhenning]

The kpoint manipulation is now implemented. I think the copy of the species routine carries too many potential side-effects to be useful for now