Fix request #7273: Files with French characters in name do not open in SVN

Also includes:
* Fix for usage of extra svn command (like annotate) that were
not working properly with utf8 files.
* Fix for sending utf8 content, files were transfered without charset. Force it
to be utf8

Change-Id: I0db90d79315367821d9be6418e7ffa6a3502d341
Merge commit 'refs/changes/12/2812/3' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  Fix request #7273: Files with French characters in name do not open in SVN
This is Tuleap 7.3.99.41

Change-Id: I114c42255c70b922b976a1e6013540e176e7b7c1