FIX: Return reference instead of copy
Select only used columns instead of all
Add new functions string.merge() and string.merge_if()
Added string.isset() function
closes #4
Add BETWEEN() macro
Added numeric.format() and numeric.from_string() functions
Added date.* functions

date.year()
date.month()
date.day()
date.encode()
date.format()
Added more date functions

date.diff()
date.now()
date.cast()
date.add()
date.sub()
Added numeric.cast() function
Use quoteIdentifier() for SQL queries
Added date.from_string()
Escape char for double quotes in literals
float, double and numeric types in lexical tokenizer
Add iif() and sys.print() functions
Add unescaped literals
FIX: remove stringstream imbue for logcmd command
FIX: small fixes for numeric.format()
Add sql.list() function
FIX: close statement in sql() destructor
FIX: sql.list() wrong loop start index