[FLINK-1223] Allow value escaping in CSV files.

Strings can now contain " quoted characters
Skip trailing whitespace after quote
The parsers are often stressed badly when reading large CSV files, so we think a lot about performance here.

I am wondering if a hash set is the best choice to check for these three elements. Computing hash, table lookup, entry lookup, comparison, ...

Might be cheaper to just hardwire the check for those types...