data.table depends to imports

[matthias-da]

according to Matt Dowle data.table will not allow a depends in future versions. Thus we should only use imports in the DESCRIPTION File and import all functionality that we need explicitly.

The data.table importing vignette now contains this text :

" Besides the Imports: field, you can also use Depends: data.table but we strongly discourage this approach (and may disallow it in future) because this loads data.table into your user’s workspace; i.e. it enables data.table functionality in your user’s scripts without them requesting that. Imports: is the proper way to use data.table within your package without inflicting data.table on your user. In fact, we hope the Depends: field is eventually deprecated in R since this is true for all packages. "

https://cran.r-project.org/web/packages/data.table/vignettes/datatable-importing.html

Another motivation is that it would be beneficial to cedta()'s awkward implementation on its last line where it needs to do the tryCatch just for packages which Depend. That line could be removed.