Dressed rdmft implementation
Adds to octopus a new routine to treat electrons interacting with one photon mode by means of the 'dressed orbital' construction. Further details can be found in https://arxiv.org/abs/1812.05562. It is necessary for the construction to add extra terms in the poisson-solver. At the moment, it only works with RDMFT.
The dressed construction allows for treating electronic systems that interact with a cavity photon mode. Details can be found in https://arxiv.org/abs/1812.05562.
- I have checked that my code follows the Octopus coding standards
- I have added tests for all the new features added in this request.