fit multiple ghosts catalogs at the same time

[bregeon]

• one beam configuration generates one catalog of ghosts
• multiple beam configurations will be acquired to better constrain the geometry
• multiple ghosts catalogs should be fit at the same time
• this means combining multiple distances to compute a Uber distance for a given geometry but multiple ghosts catalogs

[bregeon]

done in PR #64 within the fit module. May be wise to have that in the analysis module though?