Naming Convention Consistency

[THargreaves]

We should make the following naming conventions consistent:

• Particles, states, ref_traj, ref_state
• Algo and filter
• T vs K
• ws and weights (weights)
• States vs xs
• iter and k (iter in doc strings, k in loops)

[charlesknipp]

I'll put on record that I tend to more verbose naming in function args and doc strings. With that in mind...

• particles :: ParticleContainer
• particle <: AbstractParticle{T} (T will be referenced later)
• we should always use weights over ws
• states <: Vector{T}
• state :: T
• iter for "time" iteration

This is purely for function args and consistency across method definitions. Local scopes aren't much of a concern, so I have no issue using k in for loops.