respect the individual bSearchable_j options in datatables
data.options is null by default
respect the bRegex option (as well as bRegex_j for individual columns)

however, this option is not part of the initialization options, so actually users can never use it...

#400
iDisplayLength == -1 means "display all data" (#400)

we can use this feature via several ways, e.g.

- renderDataTable(..., options = list(bPaginate = FALSE))
- iDisplayLength = -1
- aLengthMenu = list(c(10, 30, -1), list(10, 30, 'All'))
make it possible to filter numeric columns based on the specified range of the form "lower,upper"