Tests for the CSV template

Problem/Motivation

Behaviour for FeedsCSVParser::getTemplate() is not yet covered. As there are sometimes feature request and bug reports for it, it would be good to have some test covering for it.

Issues for the CSV template:

• #1996240: Duplicate fields in CSV template
• #1988970: FeedsCSV parser - download template should use the default delimiter
• #2557581: CSV column names escaped & upload field double escaping.
• #2428777: The CSV template file always comes with one or more empty first rows
• #2624430: Extra permission to allow users to download the template but no need to grant the general feed permission
• #2629620: Template for TSV contains the word "TAB" instead of tabs
• #2629620: Template for TSV contains the word "TAB" instead of tabs
• #2769993: Support non-UTF-8 column headers in CSV template

Proposed resolution

Implement a test for it, covering the following cases:

1. Each delimiter: ,;TAB|+. When using the delimiter in a source key, that source key should be wrapped with double quotes.
2. Multiple mappings of the same source key: each source key should be printed once in the CSV template.
3. Special characters in source keys: & should not be converted to & for example.

Patch will follow.