Fix handling of Alceste files encoding

The encoding was not passed to AlcesteSource(). Also,
in the package, we need to distinguish fileEncoding
from encoding. By putting the former first, we preserve
backward compatibility for positional matching.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/r-temis@524 edb9625f-4e0d-4859-8d74-9fd3b1da38cb