83, add COALESCE function for better NULL handling

Now NULLs can be turned into suitable default values in SELECT statements.

Add unit test TestCsvDriver.testCoalesceFunction.
Merge branch 'master' of ssh://git.code.sf.net/p/csvjdbc/code

Conflicts:
	src/main/javacc/org/relique/jdbc/csv/where.jj
Bump version to 1.0.21-kwaxi-4