ENG-6193: Eliminate duplicate parsing code in the CSVLoader.

Consolidated the CSV file parsing code so that there is only one path for
handling errors.

Extracted the data loader from the parser.
Sped up TestCSVLoader by only starting the database once for the whole suite.
Add incorrect column count test to TestCSVLoader.
ENG-6193: Print reason instead of CSV line to the console on error.

The line content will still be logged to the report file along with the reason.
ENG-6193: Log reason and line number to console from the CSVLoader.

Instead of logging the line number and the line content to the console, print
the line number and the actual error message so that user knows what's wrong.

The line content is still logged in the report file.
ENG-6193, ENG-6145: Improve CSVLoader error messages.

- Include the column index of the column that caused the parsing error.

- Include actions in most of the parsing error messages.
ENG-6193: Addressing Anish's comments.

A bunch of cosmetic changes including method renaming, removing commented dead
code, etc.
Merge pull request #1317 from VoltDB/ENG-6193

ENG-6193: CSVLoader error message improvement.

r=akhanzode