Retain comment lines (e.g. `#`) so that they can be written out

[kinverarity1]

This causes an error at the moment but should be accommodated:

#11/15/1999 13:29:44 Updated by the Kansas Geological Survey
# #KGS#ID: 30S30W/1006347516
# #KGS#INPUT_FILE: /home/crude2_3/WellLogs/Watney/sw-ne/Kohn119a.las.las
~VERSION INFORMATION
 VERS.                          2.0: CWLS LOG ASCII STANDARD - VERSION 2.0
 WRAP.                           NO: ONE LINE PER DEPTH STEP
#
#
~WELL INFORMATION BLOCK
#MNEM.UNIT   DATA TYPE        DESCRIPTION
#---------   ------------     -----------------------------
 STRT.FT                   1684.000: 
 STOP.FT                   5898.000: 
 STEP.FT                      0.500: 

[kinverarity1]

Re-opened because lasio should be able to read in these lines, they could have important information.

creating another type of HeaderItem called CommentLineItem e.g.

CommentLineItem(mnemonic='', unit='', value='', description='', comment='# #KGS#INPUT_FILE: /home/crude2_3/WellLogs/Watney/sw-ne/Kohn119a.las.las')

This might easily enable writing them back out with LASFile.write()