Updated ContentDataStore tutorial with new CSVDataStore implementation

A new directory called csv2 was created for the old tutorial to link to. This directory contains the current geotools implementation of CSVDataStore.

In pull request #652 the unsupported module contains the new implementation for CSVDataStore which is being backported from geoserver. Thus, when both pull requests are accepted, there will be no duplication of code.

The strategy.rst file describes the new changes made in the updated implementation.