Bug fixes: 4 bugs

(1) colAgg needs return
(2) by, correctly takes care of is.factor length
(3) arraydb.to.arrayr needs to use uppercase for converting "T" to TRUE
(4) correctly handle x[,j] cases
Added plr functions
Let the result of map carry the grouped data information
Updates
Fixed lots of small bugs
Exported declare
Fixed a potential bug
Allow arguments use same type as return
Added aggregate
Fixed bugs