Morlet 1d filter bank

[lostanlen]

This PR implements:

• the AbstractNonOrientedBank and AbstractOrientedBank types, as well as their corresponding constructors.
• the Behavior concrete type.
• The AbstractFilter, AbstractFourierFilter, and AbstractFourier1DFilter types, as well as their constructors.
• The Analytic1DFilter, Coanalytic1DFilter, FullResolution1DFilter, Symmetric1DFilter, Vanishing1DFilter, VanishingWithMidpoint1DFilter leaf types, as well as their constructors.
• Operators .* and * are extended to all subtypes of AbstractFourier1DFilter.
• Same for generic functions Base.getindex, Base.maximum, littlewoodpaleyadd!, and spin.
• The method renormalize!, which carries out Littlewood-Paley renormalization in Fourier domain.
• A symmetrize! method for the Littlewood-Paley sum.
• The AbstractMeta type.
• The NonOrientedMeta and OrientedMeta leaf subtypes.
• Function of AbstractSpec that generate metadata: bandwidths, centerfrequencies, chromas, gammas, octaves, qualityfactors, scales, uncertainty.
• gauss function.
• morlet function.
• methods fourierwavelet{T<:Real}(meta::AbstractMeta, spec::Morlet1DSpec{T}) and scalingfunction{T<:Number}(spec::Morlet1DSpec{T}).
• the src/variables.jl file is replaced by src/path.jl with comparable functionalities.

Tests included.