Allow byte position tracking in CSVParser

This is a patch which adds significant modifications to the ExtendedBufferedReader.

The problem is that efficient CSV parsing requires byte positioning, not character positioning as currently provided.

The cases where byte positioning is necessary:

• Suspend/resume parsing
• Pagination/split where a large CSV file is read in chunks using file positioning.

I've found the ExtendedBufferedReader to be unable to manage bytes in its current state (relying on BufferedReader and characters), so instead I had to redesign/merge these two classes.

This modification is what we use in our system, so I'm hoping to get it released (otherwise we have to deal with custom build of Commons CSV).

Architecturally the solution might be incomplete, however it provides what I need - getBytePosition() from a CSVParser. The entire chain only works if you provide a Reader AND a charset!