Make Elgg more multilanguage-friendly

Call to devs: please, remember - not the whole world speak English. When you forgot define UT8 as charset for any output, results are unreadable for real UTF8 and we, localisators, must to rewrite again and again views. All Ajax'ed objects have this problem, all RSS have it (1.8 - too) (even than for RSS solution is obvious and stupid)... Always define UTF encoding!!!

As example

echo "<?xml version='1.0'?>\n"; - bad

<?xml version="1.0" encoding="utf-8" ?> - good