Started adding structures for the different conf sub-categories
Added conf.secondary_sources.*

Note: I also replaced L by conf.secondary_sources.size, but this has to be
introduced to a lot of other functions
removed L from wave_field functions
Updated conf.useplot to conf.plot.useplot
Added function to get SFS base path
Added a function to get spherical grid points and weihgts
Removed no longer needed equally_spaced_points_on_sphere()
Updated secondary_source_positions() to include new spherical grid
Removed get_sfs_path() from SFS_start() because the path is not set at that
moment
fixed a warning message in draw_loudspeakers()
Fixed a typo in secondary_source_positions()
Upadted to new syntax
Updated movie_wave_field function to new dimension handling
Updated config
Updated tapering_window to ignore spherical arrays
Added the possibility to get all secondary source distance at once
Updated the configuration to use substructs like conf.wfs
Added 3D to wfs_prefilter
Changed default number of secondary sources to 64
Updated ir_wfs to the newest changes