issue17:fix led model memory bug; issue19:header time is not utc bug; issue18:header data-obs\darktime\exposure time fix by shaoli's chart;add new star catalog:C6_50sqdeg_ns.py

fix bug: obs config file defined in pointing list, but not read this file, pointing obs_param is None

* Changed the name of output folder of pointing to corresponding pointing.obs_id.
* fixed the order .cat hdr updating and the creation of .cat file.
* Changed the naming of shutter and flat reference image: chip IDs now all in 2 digits.
* Updated the __init__ method of ChipOutput
* Removed Config.py from ObservationSim.Config
* Cleaned codes in ObservationSim.py, ChipOutput

remove pointing_dir, data_dir in overall_config

1.Modify fits header by defination;2.fix fgs bug: whether shutter effect open or close, fgs run error; 3. read pointinglist bug: jump the data of first row

1. add project_cycle, run_counter to config file. Modified obsid to reflect this change. Applied the same obsid to ".cat" and ".log" files.
2. limiting mags are now based on the field types (WIDE or DEEP) which can be specified in pointing list.
3. Stars are now drawn directly as PSF.
4. Reorgnaized lists of filter types in Instrument._util.

fix the crashe when use a filter that is not in the list of run_chips for mag cut. add new feature: add additional output columns to the .cat file, see NGPCatalog.py as an example