Added colAgg and rowAgg to replace c or cagg
Added docs for colAgg and rowAgg
Allowed rowAgg to take normal R objects as inputs
Fixed bugs in rowAgg
Started implementing crossprod
Finished coding of crossprod

* Added a new class db.Rmatrix

* Needs a new preview method for db.Rmatrix
Fixed bugs in crossprod
Several bug fixes
Added doc skeletons
Changed db.Rmatrix to db.Rcrossprod

Reserve the name db.Rmatrix for future use
Added array support to ops
Added support for extraction

Improved by to support bulk operations
Added unique
Fixed bugs in array extraction
Fixed more bugs in array extraction and unique
Fixed the bug in unique
Let preview view arrays properly
Added support for array in rowAgg
Fixed bugs; added support for array in preview
Added array support in all aggregates