migrate time_average to src directory

time_average adds provanance information to the output netcdf file

Author: underwoo

Makefile.am

@@ -22,7 +22,6 @@ ACLOCAL_AMFLAGS = -I m4
 SUBDIRS = lib/libnfu \
           src \
           postprocessing/split_ncvars \
-          postprocessing/timavg \
           tools/libfrencutils \
           tools/check_mask \
           tools/cubic_utils \

configure.ac

@@ -217,7 +217,6 @@ AC_CONFIG_FILES([Makefile
                  man/Makefile
                  src/Makefile
                  postprocessing/split_ncvars/Makefile
-                 postprocessing/timavg/Makefile
                  tools/libfrencutils/Makefile
                  tools/libfrencutils_acc/Makefile
                  tools/check_mask/Makefile