Add a new `lsl.sim.beam` module to help with beam models

[jaycedowell]

This PR adds a new lsl.sim.beam module to help with modeling the beam pattern of a dipole. Previously there were a few data files in lsl/data and scripts relied on their own internal implementations to convert these files into beam responses. This module replaces that by:

• moving the current beam data files into lsl_data,
• adding new beam data files that allow for the creation of Jones and Mueller matrix, and
• wrapping all of the data-to-response code into the module.