Add deconvolution methods, restructure wakefield module, and add new wake potential class

- New Wakefunction class to store a wake function object.
- New deconvolve_wp and deconvolve_imp methods were added in Wakefunction class.
- New  get-impedance method was added in Impedance class.
- New Resonator class to calculate the analytical resonator wake function.
- New Wakepotential2 class to take in wake function objects, then compute the wake potential and do the tracking.