fix bugs in handling presaved filelist version 2

enable rare datatype support for functions other than FUN_nc_merge.m

some minor updates

update readme.md: add an new example

Fix a bug related to the v2 format introduced recently

Upgrade the presaved file information created by FUN_nc_gen_presaved_…

…netcdf_info.m; This reduced 90% of the file size and speed up related functions

update comments

fix a bug which may cause out-of-memory errors

Version 1.1: add a missing file in the private folder

fix a bug: The netcdf may not be closed after reading data from it in…

… certain cases; This does not lead to errors but keeps the file occuplied by matlab.