[CSV-304] Accessors for header/trailer comments

[pedro-w]

Add accessors for header comments (before the header row)
and trailer comments (after the last record)
Also add javadoc and tests

See https://issues.apache.org/jira/browse/CSV-304

[codecov-commenter]

Codecov Report

Merging #257 (f926a30) into master (c51b595) will decrease coverage by 0.06%.
The diff coverage is 90.00%.

❗ Current head f926a30 differs from pull request most recent head ee7b3a7. Consider uploading reports for the commit ee7b3a7 to get more accurate results

@@             Coverage Diff              @@
##             master     #257      +/-   ##
============================================
- Coverage     96.99%   96.93%   -0.07%     
- Complexity      529      536       +7     
============================================
  Files            11       11              
  Lines          1166     1175       +9     
  Branches        204      206       +2     
============================================
+ Hits           1131     1139       +8     
  Misses           23       23              
- Partials         12       13       +1     

Impacted Files	Coverage Δ
...rc/main/java/org/apache/commons/csv/CSVParser.java	95.09% <90.00%> (-0.37%)	⬇️

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[kinow]

One comment, but the rest of the code looks good! Thanks @pedro-w!

[pedro-w]

I noticed that github is parsing the Javadoc annotation @since as a username. I apologize to the owner of that account.

[kinow]

Looks good to me. Asked a review from @garydgregory as he works on and knows a lot more about this component. Thanks @pedro-w !

[garydgregory]

Hi @pedro-w,
Is the intent to allow comments at the start and end of a file or before and after each record?
Please see my scattered comments as well.

[pedro-w]

Is the intent to allow comments at the start and end of a file or before and after each record?

The former. I'll explain my thinking, please correct me if I've got it wrong!

; Comment 0
A,B
; Comment 1
1,1
; Comment 2
2,2
; Comment 3

The comments attach to the following line so Comments 1 & 2 can currently be extracted from the corresponding CSVRecords and Comment 3 can never be accessed. Comment 0 is a special case. If we ask CSVParser to generate the column headings from the first record, it can't be accessed, but otherwise it's attached to "A,B" which is just a normal data record.

My intention was to allow access to Comment 0 via getHeaderComment (only in the case of generated column names) and Comment 3 via getTrailerComment (always).

I'll get onto the other issues too as they're mostly just formatting.