Update pixel readout TPC spatial resolution at r-phi plane (preliminary)

• Take "hodoscope" effect into consideration;
• The fitted parameters are based on Neff=30 and the pad pitch=0.5mm, @T2K gas, B=3T, D_{T} is close to 32.3 um/sqrt(cm) @230 V/cm Drift field;
• $\sigma_{x}$
  = 0.006001sqrt(z/10.)+0.1175exp(-0.09018*z/10.), z>=5.1mm, fitted curve
• $\sigma_{x}$
  = 0.1443-0.0047*z, z<5.1mm, linear interpolation, where sigma_x is the r-phi resolution, unit [mm], z is the driftlength, unit [mm]