The changes are now a bit more succinct with less code changes required.
Behavior is tested a little bit more thoroughly and a memory problem
when reading incomplete lines was fixed. ReadHeader also always directly
returns if header reading failed.
Error messages now are back to what they were before the change, if the
new behavior is not used.
I also tweaked the documentation text a bit.
By default, the ASCII reader does not fail on errors anymore.
If there is a problem parsing a line, a reporter warning is
written and parsing continues. If the file is missing or can't
be read, the input thread just tries again on the next heartbeat.
Options have been added to recreate the previous behavior...
const InputAscii::fail_on_invalid_lines: bool;
and
const InputAscii::fail_on_file_problem: bool;
They are both set to `F` by default which makes the input readers
resilient to failure.
