add pileup study
"subfigure package" is added in FRC_response.tex. Description about pileup study is added at Section 8.1 in Sec_Detector.tex. Four figures are added in Fig_Detector/:
FRC_correlation_matrix_5parameters.eps,
FRC_correlation_matrix_6parameters_pileup.eps,
FRC_correlation_matrix_6parameters_receff.eps, and
FRC_omega_a_precision_pileup_5parameters.eps.
(Two figures are only used in text now. I will use the remaining figures at future updates.)