Shms dc calib (#132)

* initialied script for writing individual wire tzero values into a parameter file

* script to add tzero param

* -added statement that explicitly assigns a tzero value of zero if certain criteria are not met, rather than leaving a blank line.

* -Added boolean operator to determine ribbon cable group and looped over
each ribbon cable group corresponding to shms planes DC 1U1 and DC 1U2, so far.
...Work in Progress to calculate weighted average t0 per ribbon cable.

* -script that gets tzero values per ribbon cable and writes out a param file
with the tzero values on a wire basis.

* -made few modifications (still not complete)

* -added dynamic array that holds the group value (5 or 7) for each plane

* SHMS DC Calibration script that takes the weighted average tzero per ribbon cable, and produces a parameter file containing the weighted average tzero per ribbon cable group, expressed on a wire-by-wire basis.

* -added lines to read in run number from a text file

* -added line to execute 'get_tzero_param.C' which creates a parameter
file with updated tzero values.