Model for specific lumi and IP knob sans

As discussed with @hiroyuki.nakayama already:

It would be nice to look more closely into a model for the specific luminosity

Lsp = L / Ib+ / Ib- / Nb ; where Ib+ und Ib- are bunch currents and Nb is number bunches) 

and in particular to understand if the model can capture observed effects from IP knob scans und lumi tunings.

IP knob scan PVs are

CGLOPT:IPr1
CGLOPT:IPr1d
CGLOPT:IPr2
CGLOPT:IPr2d
CGLOPT:IPr3
CGLOPT:IPr3d
CGLOPT:IPr4
CGLOPT:IPr4d

CGHOPT:IPr1
CGHOPT:IPr1d
CGHOPT:IPr2
CGHOPT:IPr2d
CGHOPT:IPr3
CGHOPT:IPr3d
CGHOPT:IPr4
CGHOPT:IPr4d

CGLOPT:Waist:Position
CGHOPT:Waist:Position



"CGLOPT:IPepx",  # IP knop tuning PVS
"CGLOPT:IPepy",
"CGLOPT:IPepyd",
"CGLOPT:IPex",
"CGLOPT:IPey",
"CGLOPT:IPeyd",
"CGHOPT:IPepx",
"CGHOPT:IPepy",
"CGHOPT:IPepyd",
"CGHOPT:IPex",
"CGHOPT:IPey",
"CGHOPT:IPeyd",

Basically, we can use lumi.py as starting point and calculate spec lumi column in preprocessing. We can switch between lumi and spec lumi just by changing the global variables OBS and OBS_unit at the top of lumi.py.