Tau conversion in ECAL and target

[tvami]

Issue description

Tasks

• As a first step do a tau gun, and measure and look at the reconstructed energy as function of energy and angle
• Do what was done in Change MG based brem vs inclusive with target biasing #63 but decay the photon to tau tau pair
• Integrate it in LDMX-SW and look at the distributions
• See if the BDT kills it?

Existing material to start off

• https://github.com/IncandelaLab/LDMX-scripts/blob/master/EnergyResStudies/electron_gun_config.py
• Source 1