reorganize corpora package; sample data for SIGIL course moved to new SIGIL package

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sigil@36 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
include BNC data sets previously available in corpora package

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sigil@37 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
all basic SIGIL data sets now included in SIGIL package; documentation still incomplete

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sigil@38 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
revised version of unit 1, now refers to SIGIL package

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sigil@39 edb9625f-4e0d-4859-8d74-9fd3b1da38cb