Merging TGC channel crosstalk parameters for A/C-sides

The channel crosstalk parameter for TGC digitization is merged between A- and C-side. This is ideally an independent parameter between side, but depending on the chamber type. Since the parameter is optimized by the Run-1 MC/Data comparison, and the side (positive and negative eta indices) was distinguished mechanically.

To reduce the memory usage, to avoid the statistical fluctuation of parameters, and to be useful for future optimization, the average between A- and C-side parameters are taken.

The parameter is still written in an ascii file, but the Condition DB is almost ready. Migration to DB is the different MR.