Added support for handing different encodings specified in HTTP Headers

Hi,

I have implemented support for **handing charset encoding**, if specified in HTTP headers. I also added a few tests to verify this improvement and that pass succesfully.

The branch is 0.5m1 as I am currently using Grails 1.3.7 for my work.

Please take a look and contact me if you have any comments.

Notes:
As I am quite new to GIT, there are quite a few whitespace changes in one file that I accidentally added to the commit. I'm sure you can resolve this on your side.

Best regards,
Dumitru