Fix importing corpus from spreadsheet file

Another change from Rcdmr 2.1 which was missed.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/r-temis@566 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Release 0.7.2

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/r-temis@567 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Increase number of characters used to detect encoding

ISO-8859-1, -15 and WINDOWS-1252 can often be confused if
special characters like œ or € do not appear at the beginning
of the text. From experimentations, it looks like ICU will
use up to around 10000 characters, so load more than that
just in case.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/r-temis@568 edb9625f-4e0d-4859-8d74-9fd3b1da38cb