Implements FR #2405. Extensive tests added.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1254 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Implements FR #5465. Test added + News updated.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1255 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Squashed commit of the following:

- Minor fix to anyDuplicated
- Closes bug #5437. `by=.` cols now don't lose attributes when used in `j`. Better tests added to catch further regressions. News updated.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1256 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Updated NEWS alone.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1257 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Closes bug #5415. .BY gets names attribute set properly.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1258 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Closes #5527. Related to #5423. More tests added. News Updated.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1259 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Closes #5443. 'get' sees i's columns during join. Tests added and News updated.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1260 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Fix for #5583. Handle expressions properly in DT[order(.)]. Tests added.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1261 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Fixes #5582. edge case for unique and duplicated, handles empty data.tables correctly.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1262 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Closes #5519. dcast.data.table now runs fine on packages that imports data.table as well. NEWS updated.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1263 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Closes #5675 (column order when formula has … in RHS) ad #5676 (documentation for dcast).

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1264 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
merge(x, y, all=TRUE) error when 'x' is empty dt is now fixed. Closes #5672.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1265 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
rbindlist gets use.names and fill argument, and all implementation moved to C. Closes #5612, #5158, upgrades #4790 as filed in #5249.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1266 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Updated NEWS.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1267 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Minor typo fixes. No changes to code.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1268 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Closes #5647. `DT[, LHS := RHS, by=.]` doesn't segfault now when length(RHS) > .N  for any/all groups.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1269 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Better (and consistent) handling of duplicate names during subset. Closes #5008 and $5688.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1270 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Merge branch 'master' of https://github.com/arunsrinivasan/datatable