Draft: Added new files for tau2KS0mu and tau2KS0KS0mu decays (from c and b quarks)

MR related to the implementation of six new DecFiles to simulate the following LFV tau decays:

EventType	Decay chain
23513128	c\to D_{s}\to\tau\nu_\tau,\;\tau\to K_s^{0}(\pi^+\pi^-)\mu
23513129	b\to D_{s}\to\tau\nu_\tau,\;\tau\to K_s^{0}(\pi^+\pi^-)\mu
31113148	b\to \tau\to K_s^{0}(\pi^+\pi^-)\mu
23515130	c\to D_{s}\to\tau\nu_\tau,\;\tau\to K_s^{0}(\pi^+\pi^-)K_s^{0}(\pi^+\pi^-)\mu
23515131	b\to D_{s}\to\tau\nu_\tau,\;\tau\to K_s^{0}(\pi^+\pi^-)K_s^{0}(\pi^+\pi^-)\mu
31115149	b\to \tau\to K_s^{0}(\pi^+\pi^-)K_s^{0}(\pi^+\pi^-)\mu

Each DecFile implements generator-level selections on GP, GPT, GTHETA of the final state particles and a selection on the presence of a given type of quark (c or b) among the \tau ancestors, based on the required decay chain.