csvrows - bug fixes and added random row support

Fixed some range expression bugs, added tests, now supporting ranges expressions like 11-13 as well as colon notation of 11:13. Range expressions can be compound expressions e.g. 1,2,8-10 or 1,2,8:10.

Fixed output bug on csvrows. If no rows expressions provided and input is read from standard in then all rows will be written back out (validated through go's csv encoder/decoder). Show header option now respected correctly in csvrows.