Missing redirections & Wrong temp files handling

- In some error cases, the upcontent.php and upicon.php pages didn't
redirect the user
- Got rid of the dirty and unsafe temp file creation: now using
move_uploaded_file
Automatic translation of a homebrew when created

- When an entry is created, its short and long description are
automatically translated to the supported languages. If the entry is
then modified, the translations aren't updated because it could mean
loss of contributors translations (coming soon feature)