Support for ignoring some columns in configuration file when CSV file has no header line.

[nianiaJR]

As your README said:

Note: The order of properties in the above props must be the same as that of the corresponding data in the CSV data file. If I have a file course.csv:

name,        teacher,          id
math,         Mr Liu,           1
computer,  Mr Wang,      2

I don't want the first two field name and teacher, only want to import the id field. How can I promise the order of the props in the config? Or I only need to add the :IGNORE field to the csv file? Is there a option like this:

...
vetex:
tags:
- name: couse
props:
- ignore: true  // Add this field support，meaning to ignore the relative order field in csv.
- ignore: true
- name: id,
type: string
...

thanks

[yixinglu]

Good point! This implementation is on the way.