vtkDelimitedTextReader improvements

Preview

vtkDelimitedTextReader offers a GetPreview method to inspect the file content. During the RequestInformation pass, it reads the PreviewNumberOfLines first lines of the input file. By default, nothing is done and Preview is empty.

This is useful to configure the reader options (like XXXDelimiters or HaveHeaders) before the RequestData pass.

SkippedRecords

The new SkippedRecords option allows to skip the first N records (usually lines). This is useful as some file format may contain non standard header lines. See for instance the gslib format.

Comments

vtkDelimitedTextReader supports the concept of comments: starting at on of the given CommentCharacters, the remaining data of the current record is skipped.