Added index.php files for security purposes in these directories:
- "Themes/default/images/theme"
- "Themes/default/images/membericons"
- "Themes/default/images/admin/big"

Signed-off-by: Xarcell <xarcell@yahoo.com>
Merge branch 'release-2.1' of https://github.com/Xarcell/SMF2.1 into release-2.1