Fix tab before multi line TXT string

[pjjonesnz]

Ignore tabs before the start of the string in a multi line TXT record
Add exception if multi line is still open when function ends

If there are tabs at the beginning of the second (or subsequent) lines in a multi line TXT record, the tokenizer only returns the first line of text. It correctly ignores space and newline, but currently doesn't ignore tab.

While this may not be too widespread, the functions that DirectAdmin (server management software) uses to create TXT records inserts tabs at the beginning of the second (and subsequent) lines of a multi line TXT record, and as DirectAdmin is widely used it would be nice to be able to support this.

[pjjonesnz]

Here is the Direct Admin page where it shows how their txt records look. However note that the whitespace in their example is created using tabs.

https://help.directadmin.com/item.php?id=552

[pjjonesnz]

I've updated the txtExtractor and extractCharSet functions to use the AsciiChar class.

Have also modified the code so that quotes are not required around a txt record as per RFC1035

character-string is expressed in one or two ways: as a contiguous set
of characters without interior spaces, or as a string beginning with a "
and ending with a "

Have updated the "hell" test file txt records to reflect these possibilities and all tests still pass.