Add a trailing semicolon to the Categories= line in evopedia.desktop

The Categories= line in evopedia.desktop needs a trailing semicolon, see http://standards.freedesktop.org/menu-spec/latest/ar01s03.html

P.S.
I'm packaging evopedia for Gentoo (this is why I found out this little problem), more news soon.
Merge pull request #3 from poletti-marco/master

Add a trailing semicolon to the Categories= line in evopedia.desktop