Added mime type control on uploaded files

Only images and pdfs are now allowed.
Fixed breach in POST/GET vars

Added simple mysql_real_escape_string on POST and GET vars.
Fixed breach in POST/GET vars
Merge remote-tracking branch 'upstream/master'

Conflicts:
	core/plugins/ajaxupload/ajaxupload.php
	core/slash.php
Merge pull request #33 from lowki/master

Fixed vulnerability on ajax file upload.