Fix for #5366 - setkey works properly on data.table containing list columns. Tests added.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1216 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
A new separate `?setDT`. Cleaned up `?setkey`.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1217 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Closes #5408 - order of columns were sometimes reversed with as.data.table.table. Tests added.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1218 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Minor corrections to '?setorder'.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1219 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Added type name to error message in Creorder

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1220 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
'setorder' now retains key if order doesn't change.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1221 edb9625f-4e0d-4859-8d74-9fd3b1da38cb