Rename ATDF writer to Text writer

[minhhaiphys]

The AtdfWriter function and stdf2atdf script convert STDF to its text representation, not exactly in ATDF format (which has somewhat different specs from STDF). To avoid misunderstanding, I propose to rename them to TextWriter and stdf2text respectively.

One more minor change to allow users to convert STDF to a text file, instead of parsing all the text to the screen.

[cmars]

If AtdfWriter isn't producing valid ATDF anyway... would a CSV format be more generally useful than pipe-delimited?

[minhhaiphys]

Since arrays are converted to comma delimited, CSV for the entire STDF would cause difficulty for user to load CSV to other analysis tools such as Excel. So pipe delimited would be the easiest. Alternatives can be semicolon, colon. Another option is giving user the choice by adding a kwarg such as delimiter='|'

I do have functions to import STDF into list of text/dictionary/DataFrame object and script to export to Excel, which I use for analysis. If you're interested in having those into the master, I'll create another merge request.

[cmars]

I do have functions to import STDF into list of text/dictionary/DataFrame object and script to export to Excel, which I use for analysis. If you're interested in having those into the master, I'll create another merge request.

That'd be most welcome, thanks!

[cmars]

The delimiter kwarg would be a nice followup.