Feature improvement: get_energy_landscape to retrieve state vibrational frequencies

[lopeztarifa]

Dear SCM developers,

I was wondering if the function get_energy_landscape could be improved so there is an easy (method state.frequencies?) to access the vibrational frequencies of each state.

So far I managed to get them by looping the get_frequencies function on the states, but it is annoying as I have to select the right file name for the engine argument. I hope you can improve it.

Thanks,

[nfaguirrec]

Dear @lopeztarifa,

I'll take a look at it!

Best, Nestor