String macros for spin-orbitals and spin-configurations

[jagot]

I find that I miss these from time to time, i.e. so"1s0α" and sc"1s0α 2p-1β", or something along those lines. Ties in with #24 and #36. #21 should probably be resolved before, to reduce confusion (alternative notation for the m quantum number of a spin-orbital could be e.g. sc"2p(-1)β").

[mortenpi]

The macro for orbitals was added in #88, but a macro for configurations is still on the TODO?

[jagot]

That's right; I wanted to generalize the current functionality for parse strings into configurations:

AtomicLevels.jl/src/configurations.jl

Lines 345 to 363 in 07120dc

	function Base.parse(::Type{Configuration{O}}, conf_str::AbstractString; sorted=false) where {O<:AbstractOrbital}
	isempty(conf_str) && return Configuration{O}(sorted=sorted)
	orbs = split(conf_str, r"[\. ]")
	core_m = match(r"\[([a-zA-Z]+)\]([*ci]{0,1})", first(orbs))
	if core_m != nothing
	core_config = core_configuration(O, core_m[1], core_m[2], sorted)
	if length(orbs) > 1
	peel_config = Configuration(parse_orbital.(Ref(O), orbs[2:end]))
	Configuration(vcat(core_config.orbitals, peel_config.orbitals),
	vcat(core_config.occupancy, peel_config.occupancy),
	vcat(core_config.states, peel_config.states),
	sorted=sorted)
	else
	core_config
	end
	else
	Configuration(parse_orbital.(Ref(O), orbs), sorted=sorted)
	end
	end

to work with spin-configurations as well, but I got a bit stuck.