charset: utf8 support

[thriqon]

Problem

Attachments are uploaded with empty charset. Special characters (i.e. non-ascii) are stored with the wrong charset.

Steps to Reproduce

kanso.json:

"attachments" : [ ... "test.js" ... ]

test.js:

alert('ä');

I'm not sure if all files should be treated as utf8, but at least modules.js is...